A number of congruences can and have been found to exist between the process philosophy of Alfred North Whitehead and Buddhist thought. The present series of articles is made possible only because of these congruences and the great potential for philosophic cross-fertilization which they suggest. One of the points, however, at which congruence seems to disappear is the basic one of the validity of speculative philosophy itself, particularly when the Maadhyamika form of Mahaayaana Buddhism is considered. Both the Maadhyamikas and the closely related Praj~naapaaramitaa [Perfection of insight]  tradition -- both here referred to as Praj~naa Buddhism  -- are characterized by a thoroughgoing program of invalidating conceptual thought: the former through the use of logical paradox, and the latter through what might be called rhetorical paradox.  Conceptual thought of any kind is relegated by Praj~naa Buddhism to the level of "conventional truth" (sa^mv.rtisatya), which is essentially delusive or false when seen from the standpoint of "ultimate truth" (paramaarthasatya).
On the other hand Whitehead's program is premised on the inherent validity of conceptual thought:
Speculative Philosophy is the endeavor to frame a coherent, logical, necessary system of general ideas in terms of which every element of our experience can be interpreted. 
The elucidation of immediate experience is the sole justification for any thought; and the starting point for thought is the analytic observation of components of this experience. 
That we fail to find in experience any elements intrinsically incapable of exhibition as examples of general theory, is the hope of rationalism... It is the faith which forms the motive for the pursuit of all sciences alike, including metaphysics. 
The bases of success in the imaginative construction of an adequate metaphysical system are, first, its derivation as "generalization of particular factors discerned" in the rich variety of human experience,  and second, its "unflinching pursuit of the two rationalistic ideals, coherence and logical perfection." 
We are talking then, apparently, about two diametrically opposed programs of endeavor, one as antiintellectual as the other is intellectual. When we look more deeply at both of these, however, there seems to me to be two routes to follow in seeking a connection between such a speculative metaphysical philosophy as Whitehead's and Praj~naa Buddhism. One of these routes is to examine the notion of relative validity of systems of thought on the level of Buddhist "conventional truth." The other is to explore the strikingly non-dualistic language of the Praj~naapaaramitaa Suutras, specifically that of the A.s.tasaahasrikaa Praj~naapaaramitaa [The perfection of insight in eight thousand lines]. 
Naagaarjuna's basic statements in chapter 24 of the Madhyamakakaarikaas regarding the status of conventional truth are well known: The teaching of the Dharma rests on the two truths, that of the world's convention (lokasa^mv.rtisatya) and what is truth ultimately (paramaarthata.h). Although there is a profound distinction (vibhaaga) between the two, the ultimate truth, and hence nirvaa.na, cannot be attained without resorting to that other truth based on common usage ("transaction": vyavahaara).  Naagaarjuna proceeds to show that the conventional doctrines of Buddhism (the Four Aryan Truths, Buddha, Dharma, and Sangha) as well as all commonsense truths (that doers do things, things come to be and pass away, etc.) are, in fact, logically validated only by means of the principle of dependent origination or emptiness:  "Everything holds (fits with, is logically consistent with: yujyate) for that for which emptiness holds; nothing holds for that for which emptiness does not hold."  The coherency of transactional truth turns out to be founded upon the premise of correlativity. But this very coherency is itself ultimately undermined by the same premise when it is systematically applied to the separate concepts which transactional truth depends upon. They are ultimately not to be depended upon simply because they are "empty" fabrications of the depending (upaadaana) mind. These fabrications are the discriminations (vikalpa: is/is not, permanent/impermanent, bondage/release, sa^msaara/nirvaa.na, not empty/empty, etc.) which are the conceptual and verbal proliferation (prapa~nca) which sustains the painful affliction (kle`sa) of the depending mind.  The doctrine of emptiness was provided by the Buddhas as a remedy for all views,  including emptiness itself: "Neither 'empty' should be said, nor 'not empty', nor 'both' nor 'neither' -- but they are said [anyway] for the sake of designation (praj~napti).  Thus all transactional truth (vyavahaarasatya), valid as such owing to its correlativity, is invalid from the ultimate standpoint of nirvaa.na or enlightenment -- and it is the essential premise of transactional truth, dependent origination, which provides the means by which transactional truth is transcended.
Although Naagaarjuna does not explicitly specify what the valid standards (pramaa.na) of transactional truth are,  it can easily be shown that he makes use of at least the three pramaa.nas of direct perception (pratyak.sa), inference (anumaana), and authoritative tradition (aagama) throughout his writings. This is most clearly shown in chapter 24 of the Madhyamakakaarikaas, where inference is used to show a logical coherence between the concept of dependent origination, conventional Buddhist doctrine (that is, aagama), and conventional common-sense perceptions and inferences regarding the world. Conventional Buddhist doctrine is thus seen to be reasonable, and conventional common-sense notions can be reasonable too. But truth for Naagaarjuna is ultimately a pragmatic concept: "Truth is in reality not what has issued forth without contradiction
from [the mouth of] a sentient being: truth is solely what is for the welfare of others (paraikaantahita). Its opposite is falsity, because of its being detrimental (ahitatva)."  Hence the truth-value of what is transactional is simply its effectiveness as a means (upaaya) to nirvaa.na. But the effectiveness of transactional truth is inseparable from its rational coherence, and as Naagaarjuna shows, it is this very rational coherence which dialectically puts transactional concepts to rest (upa`sama). In this sense the real truth-value of transaction is its inherent falsifiability. It is this fundamentally paradoxic standpoint which, of course, seems to give little encouragement to any program of speculative philosophy.
Candrakiirti (7th century),  representing the Praasa^ngika school of the Maadhyamikas, stoutly maintains the principle of discontinuity between the two levels of truth: conventional truth leads beyond itself only by virtue of the fact that its conceptual-linguistic components dissolve into incoherency when scrutinized by means of the very premise of coherency, dependent origination.
For Candrakiirti all things (bhaava) bear a twofold nature (svaruupa or svabhaava). One of these is constituted by that which is the object (vi.saya) of right vision (samyagdar`sana) and the other by that which is the object of false vision (m.r.saadar`sana) of those whose intellectual eye (blo'i mig) is completely covered by ignorance.  The latter -- the false vision of conventional truth -- is indeed valid, according to the world, if it is the perceived object (graahya) of what the world considers the six sense-faculties to be when these are free of impairment by sickness, drugs, spells, deceptive stimuli (such as echoes, reflections, mirages), etc. The sixth faculty, mind (manas), is subject not only to the malfunctions of the other five, with whose perceptions it must deal, but also to the damage caused by the doctrinal systems and views (siddhaantaadi) presented by those who are "not right" (ya^n dag pa ma yin pa) as well as by fallacious reasoning (anumaanaabhaasa). 
Candrakiirti says that what is imagined (kalpita), based upon illusion or mirage, as well as what is imagined by non-Buddhist theorizers (tiirthika) are both nonexistent from the world's point of view. Theory -- such as the three-gu.na theory of the Saa^mkhya -- is classed with illusory appearances because those who engage in it, although they do "desire to gain access to reality, they desire to reach that supreme point through correct determination of the true [nature] of the birth, destruction, and so on, of things which are recognized even by ignorant persons such as cowherds and women."  There is no way to get closer to reality by improving upon ordinary conventional truth. The only thing such theorizers arrive at, according to Candrakiirti, is a terrible fall into "the ravine of bad views." And he advises even the Buddhist theorizer (in the present case a logician of the school of Dignaaga): "Let this conventional [truth] be! It exists as embodiment beset by error alone. [Yet] it is the cause of
accumulation of wholesome roots which lead to release for those who desire it -- up until their discovery of reality (tattvaadhigama)." 
The ultimate truth cannot be put into words (anabhilaapya) and is not an object of knowledge (na j~naanavi.saya) -- it is to be personally experienced (svasa^mvedya):  "In that ultimate how could there be any activity of words or of knowledge (j~naana) For that ultimate is without conditions apart [from itself] (aparapratyaya), quieted, to be personally experienced (pratyaatmavedya) by Aryas, transcending all concept-proliferation. It cannot be taught, nor can it be known (na j~naayate)."  Hence where ultimate reality is concerned "the Aryas  themselves are the pramaa.na." 
Thus there can be no real conflict between the world's truth and the ultimate truth; conflict with the world can arise only when one denies something which is recognized as valid by the world.  When the Maadhyamika denies the validity of the concepts recognized by the world, he does so not merely because he speaks from the ultimate standpoint, but also because he is out to show that the invalidity of those concepts derives from the very nature of conventional truth, that is, its dependent origination, and thus the procedure of dialectic refutation is really an exercise of transactional truth based upon recognized conventions of logic (anumaana) and ordinary perception (pratyak.sa).  The target of refutation is made up of the concepts both of the everyday world as well as those of Buddhist teaching -- in other words, the pramaa.na of authoritative tradition or scripture (aagama) is included within the realm of conventional truth. 
Beyond the valid -- but ultimately delusive -- pramaa.nas of conventional truth, we find a sort of ultimate pramaa.na: the Aryas themselves, or more accurately perhaps, their personal experience of enlightenment. This ultimate standard, however, is truly empty: a state of silence (tuu.s.nii^mbhaava) out of which there arises no concept-proliferation and hence no assertions or denials.  This is the non-viewpoint of the ultimate truth of which Naagaarjuna ironically says, "Those for whom there is really non-existence (i.e. the Maadhyamikas), who because of their reliance upon enlightenment [rely on] no assertion, no [special] conduct, no thought -- how can they be considered nihilists?"  Nihilism (naastikatva), like its opposites, is a position taken within conventionality, whereas ultimacy is a mode of experience which does not take any position nor deny any position -- the positions deny themselves.
My conclusion is that for Naagaarjuna and for Praasa^ngika Maadhyamika,  the philosophic program adumbrated at the beginning of this article is devoid of truth-value. The endeavor to interpret experience, to explore and extend the powers of rationality, does not in itself lead to the goal of nirvaa.na. Even if speculative philosophy can satisfy the epistemological canons of conventional truth, from the ultimate standpoint, it has no more truth in it than does a mirage or spots before the eyes. I think another possible evaluation of constructive philosophic thought can be linked with the teaching of the earlier Praj~naapaaramitaa tradition, however, and it is to this that we now turn.
The stated purpose of the Perfection of Insight as a teaching is essentially the same as that of Naagaarjuna -- getting rid of attachment:
This dharma is taught for the sake of not-taking-hold (anudgraha) of any dharma -- yet the world carries on taking-hold. 
... This perfection of insight is presented for a great purpose: for [bringing about] non-acquisition (aparigraha), for [bringing about] non-addiction (anabhinive`sa) 
Such a program aims at the elimination of a mode of experience, that is, experience qualified by attachment. The goal is a detached mode of knowing -- perfect insight or enlightenment -- which is described in negative terms:
The Tathaagatas' non-attachment-knowing (asa^ngaj~naana) is indeed perfect insight. 
Non-apprehension (anupalambha) of any dharma is the perfection of insight. Thus it is said that when there is no idea (sa^mj~naa), name (samaj~na), designation (praj~napti), or conventional language (vyavahaara) -- then [there is] perfect insight. 
This is that perfection of insight -- no supposition (manyamaanataa) about any dharma at all. 
From this we gather that the unattached mode of knowing real things (dharmas) is a mode of knowing without conceptualization. Insofar, then, as any real thing is conceived or talked about, it is known in the attached mode and is thereby falsified. Dharmas or dharmataa (real-thing-hood, the nature of reality) as conceived, schematized (for example, in abhidharma thought), and talked about are fabrications (kalpanaa):
For those dharmas are not there in the way that untaught, simple people are addicted to them... The way they are not there is the way they are there. Thus they are not-being-there (avidyamaana), so they are called ignorance (avidyaa). Untaught, simple people are addicted to them. All dharmas, not being there, are fabricated (kalpita) by them. Having fabricated them they are attached to the two extremes (existence and non-existence, etc.) and neither know nor see those dharmas [as they really are]... Having fabricated them they become addicted to the two extremes. Having become addicted, and relying on that source as [a basis of] apprehension, they fabricate past dharmas, future dharmas, present dharmas. Having fabricated these they become addicted to name and form (the five bundles)... Fabricating all those dharmas which are not there they neither know nor see the Path as it really is... They do not go forth from the triple world. They do not wake up to the true end (bhuutako.ti, i.e. ultimate reality). 
Attachment is by means of both name (naama) and sign (nimitta)... [Thinking,] "form and the other bundles are empty" -- this is attachment. [If] one entertains the ideas "past dharmas" with regard to past dharmas, "future dharmas" with regard to future dharmas, "present dharmas" with regard to present dharmas -- this is attachment. 
The term "dharmas" is here necessarily ambiguous. Its basic function is to designate something real or valid. Thus dharmataa refers to the nature of all that is real, what constitutes actuality. But "dharma" is itself a word, and when dharmas are named - form, consciousness, bodhisattva, nirvaa.na, or whatever -- they are totally within the sphere of the attached mode. It is in this sense that "all dharmas are made up by fabrication."  At the same time the terms "dharma" and "dharmataa" are used to refer to what is ultimately real, apart from fabrication: "All dharmas are talked about only by means of names, only by means of [linguistic] transaction (vyavahaara). But the transaction is nowhere, is out of nowhere, is not a transaction at all: all dharmas are free of transaction. free of talk, not transacted, not talked about." 
The skill-in-means (upaaya-kau`salya) of the bodhisattva is both to perceive signs -- the images, ideas, and names mentally abstractable from experience -- and to develop his awareness of the signlessness of reality as it is ultimately.  This is an expression of the doctrine of the two truths, conventional and ultimate, applied in a way which reveals the bodhisattva to be a being "in this world but not of it." It is this skill-in-means which enables him to operate in the two modes simultaneously. However, because he does remain in the unattached mode, he is not karmically bound to those experiences which are normally in the sphere of attachment: "He cultivates, devotes himself to, and honors forms, sounds, odors, tastes, touches" -- but he does so because, in fact, he has "overcome" (abhibhuuya) these, he has no attachment or objective supports (aaramba.na), and his acts thus arise out of skill-in-means. 
Conventional or transactional truth includes the entire realm of discourse, not only what is invalid in relation to Buddhist discourse but Buddhist discourse as well:
In reality no distinction or difference between [any of] these dharmas can be apprehended (na upalabhyate). As talk are they described by the Tathaagata ... "empty," or "signless," or "wishless." or "without formation," or "non-arising," or "without birth," or "non-existence," or "dispassion," or "cessation," or "nirvaa.na" -- these are [just] talked about ... All dharmas whatever are beyond talk (anabhilaapya). 
"Perfection of insight" -- this is only name-giving. And [the possibility of validly asserting:] "that name is this [actual thing]" cannot be apprehended. We say that the name has only speech as its object-of-reference, while that perfection of insight is neither found nor apprehended: just as it is a name, just so is it perfection of insight; just as perfection of insight is, just so is the name. A duality of dharmas here is neither found nor apprehended. 
The actual reference of the word "perfection-of-insight" is not to a real thing but to a speech-thing, verbalized reality -- or as the commentary says, the term just reflects the discrimination (vikalpapratibimbaka) of the attached mode. The real thing which is being talked about, that is, the state of perfect insight, is not capable of comparison with the name or concept, since names can only be compared with names -- and it is only when there are no names that the reality of
perfect insight is found. Even the negative language associated with ultimate truth has finally to be seen in this light:
Non-arising (anutpaada) appears to you to be talked about, but this same non-arising is [only] talk. 
Form is unthinkable and so are the other bundles. [When a bodhisattva] does not even entertain the idea "form is unthinkable," he proceeds in the perfection of insight... 
The nonattached mode of knowing is present when one "proceeds but does not arrive at [the considerations] 'I proceed', and 'I will proceed' because all dharmas are neither arrived at nor depended upon [in reality]. This is the bodhisattvas' samaadhi called 'non-dependency upon any dharma (sarvadharma-anupaadaana).'"  This mode is spoken of as "standing in emptiness,"  which is where the Tathaagata stood and where all those who follow him should stand -- precisely nowhere at all -- because his mind was not fixated (aprati.s.thitamaanasa) by any conceptualized dharma or consideration. 
The inevitable conclusion is that what is so for the unattached mode has nothing to do with understanding, hence the paradoxic rejoinder by Subhuuti to those who find the teaching on the perfection of insight difficult to understand: "It can't be understood, it can't be understood (na vij~naayate) ... for in it nothing at all is pointed out, nothing at all is learned."  And as there is no dharma at all pointed out, illuminated, or communicated no one will ever gain the perfection of insight from Subhuuti's teaching of it. 
Looked at from this paradoxic angle, that is, from the point of view of ultimate truth, all doxa -- the points of view of transactional truth -- are equally mere fabrications, none of which can be said to be even relatively adequate to express or describe perfect insight, since the latter is not "available" for comparison with its linguistic descriptions. We are apparently no closer to a possible link between conceptuality and enlightenment, intelligibility and nirvaa.na. But from the very discontinuity between the two, there emerges an interesting corollary: while on the one hand the real and the fictive, or fabricative, cannot be distinguished because distinguishing is itself conceptual, on the other hand what fabrication, discriminations, concepts really are is, in fact, the perfection of insight:
This perfection of insight cannot be taught or learned or distinguished or considered or demonstrated or reflected upon by means of the bundles or by means of the elements (dhaatu) or by means of the sense-fields (aayatana). The reason for this is the isolation (viviktatva) of all dharmas, the absolute isolation of all dharmas... But the perfection of insight is not to be understood apart from the bundles, etc. The reason for this is that it is just the very bundles, etc., which are empty, isolated, quieted. For thus are the perfection of insight and the bundles, etc.: a non-duality which is without division and cannot be apprehended because of its emptiness ... its isolation ... and hence its being quieted. 
This nondual nature is referred to in quasi-positive terms as "suchness" (tathataa):
The Tathaagata knows form (and each of the bundles) as suchness... The suchness of the bundles is the suchness of the world; the suchness of the world is the suchness of all dharmas... This is all just one suchness which has left behind the manifold [states] of existence and non-existence, because it is not one, not many, not disappearing, without modification, without duality, undivided. 
This one suchness of all real things is also identical with perfect insight, the state of enlightenment: 
Because of the boundlessness of objective supports (aaramba.na: intended object), this perfection of insight is a boundless perfection. Because of the boundlessness of sentient beings this perfection of insight is a boundless perfection. Because all dharmas are without a beginning, middle, or end this perfection of insight is a boundless perfection. 
"The absence of own-being (svabhaava) in beings should be known as the nature of the perfection of insight."  The absence of own-being (that is, independent self-existence) in beings demonstrates the absence of it in the perfection of insight. Similarly their isolation, unthinkability, indestructible nature, and the fact that they are not in the process of becoming enlightened -- all demonstrate the same for the perfection of insight. 
If then the nature of reality is not different from enlightenment, then the nature of reality must share the unattached, nondepending, nonapprehending character of enlightenment. A hint of this can be seen in two of the terms often associated (as above) with `suunya (empty), namely, vivikta (isolated), and `saanta (quieted). Both of these seem to have their origin in the language of meditation proper: the isolation or separation of the meditator from his conceptual and emotional "connectedness" with his normal social world, followed by his development of inner quiet or tranquility (`samatha, upa`sama, etc.). With the Perfection of Insight tradition these subjective aspects of disconnectedness and tranquility are said to be the ultimate nature of all real things. 
The ultimate nature of reality shares in the disconnectedness which characterizes the perfection of insight. Since this insight is unattached knowing, the Tathaagatas
Demonstrate Dharma to beings for the sake of non-clinging (a`sle.sa) íK The non-connection (asa^mbandha) of form (and the other bundles) is the non-clinging of form ... The non-connection of form is form's lack of origination and cessation ... In this way non-clinging comes to be, as a result of knowing and seeing that all dharmas are not clinging, not connected. 
This common nature leads to further implications. Perfect insight is not different from the real nature of those characteristics of the attached mode which, conventionally, the perfection of insight is supposed to eliminate:
This is the perfection of non-discipline (avinaya), because there is no apprehension of past, future, and present goals.
This is the perfection of non-affliction (asa^mkle`sa), because there is no own-being to greed, anger, and delusion.
This is the perfection of dispassion, because there is no falseness in any dharma.
This is the perfection of non-arising, because there is no discrimination in any dharma.
This is the perfection of non-discrimination, because of its identity with discrimination (vikalpasamataa).
This is the perfection of suffering, because the nature of dharmas is like space. 
Distracted thoughts are thoughts distracted from the nature of dharmas (dharmataa). But such thoughts when seen as they really are by insight are without [intrinsic] characteristics and are in reality not distracted. Indeed, those thoughts are by nature brightly clear (prak.rtiprabhaasvara). 
After all, if it is all dharmas which share the same nature, suchness, with the perfection of insight, then such unwholesome (aku`sala) dharmas as anger, delusion, discrimination, distraction, suffering, etc. are not to be excluded.
Finally, there is the clear implication that it is the given nature of things which is identical with the perfection of insight, and therefore this insight is not something which has yet to be attained by the striving bodhisattva. Enlightenment, in short, is what the bodhisattva already really is:
The [meditative] actualization (bhaavanaa) of the perfection of insight is an actualization of space. Homage should be paid to those bodhisattvas who put this armor on, for he who fastens on his armor for the sake of beings seeks to be armed with space ... For the sake of beings who are [themselves] like space, like the dharma-realm, he seeks to be armed, he seeks to become fully enlightened. He seeks to liberate space, he seeks to get rid of space. 
He will make efforts about space, about wide-open space, who thinks of being trained in or of making efforts about the perfection of insight. 
Deep is the perfection of insight: it is not actualized by anything, for no one actualizes it ... nor is there anything to be actualized ... anywhere. The actualization of the perfection of insight is actualization of space, of all dharmas, of non-attachment, of the limitless, of non-existence, of non-acquiring. 
The nature of things is not something which requires actualization: space is empty without needing to develop that emptiness. In exactly the same way the perfection of insight is not in need of development. The implication is evident that the essential original nature of thought (citta), brightly clear, as well as the nature of things in general, is unattached knowing, the perfection of insight which constitutes buddhahood:
The nature of all dharmas is complete purity ... All dharmas have attained nirvaa.na, [and hence] are identical with suchness ... All dharmas are noble arhats, completely purified by nature ... All dharmas are enlightenment because they cause one to be aware of the buddha-knowing (buddhaj~naana). 
Let us now consider from this particular perspective Whitehead's own non-dualistic approach to the topic of knowing or perception. Perception for Whitehead is basically another name for reality itself. An actual occasion is a process of concrescence, growing together, of many objects into a novel subject, by means of those prehensions of objects which together constitute the new actual occasion. The actual occasion is its prehensions, and the objects of prehension are the subject in its process of actualization. From this standpoint all that actually exists is the subject: "Apart from the experience of subjects there is nothing, nothing, nothing, bare nothingness."  Objects are only constituted by (or as) the prehensions, feelings, perceptions of the subject as it enacts itself.  In other words, "that moment of experience, in its character of being that one occasion, is nothing else than the percipient [subject] itself." 
Now the "experiences of subjects" are simply prehensions, perceptions; and the analysis of prehension  shows that it consists of the subject, the object(s), and the manner in which the object is felt or perceived by the subject. Yet this is only analysis, and reality is the synthetic concrescence, as a unity, of an actual occasion. The perceptual experience, an act of knowing, is thus a single, undifferentiated whole; there is, in fact, no object as such, external to the subject, nor a subject separable from its object(s), nor a process of perceiving which a subject "has" with regard to an object. The threefold analysis does reflect, on the other hand, the manner in which the world is apparently experienced by most people most of the time -- a manner which the very language of the preceding words of this sentence renders in typical form: People (that is, subjects) experience a world. My point is that there is an implicit parallel here for the Mahaayaana doctrine of two truths: Whitehead's metaphysic indicates an "ultimately" nondual reality which is "normally," that is, analytically or conceptually, experienced as a manifold "world" in which the many subjects severally experience each other as objects.
I think that we can find a possible reason in Whitehead's own discussion of perception for the kind of dichotomy just suggested. Whitehead describes three modes of perception: causal efficacy, presentational immediacy, and the mixed mode of symbolic reference.
Perception in the mode of causal efficacy is simply the prehension which constitutes the concrescing subject itself as well as the objectified "data" in relation to which the subject is the emergent, novel occasion. It is the subject's experience or awareness of the objective background of which it is the subjective result. In this sense, what the subject is, is what it perceives (prehends).
Conscious perception, a feature of prehension which seems to appear only in more complex organisms, allows for the mode of presentational immediacy, which is sensory perception in the sense that the term "perception" is ordinarily used: sounds, smells, colors, tastes, and bodily feelings (touch, kinesthesia,
pain, etc.).  Three aspects of presentational immediacy should be noticed here.
First, it is a phase of perception in the mode of causal efficacy, not a generically separate mode of perception. The objective side of prehension becomes sense objects, sense-data, for the subject to the extent that this mode of perception is possible for it, but what is experienced as sense-perception is already experienced (prehended) in a more immediate way as causal efficacy, that is, prehension which constitutes subject and object as one occasion.
Second, therefore, presentational immediacy shares the ontological non-duality of causal efficacy -- the world which appears does so by virtue of sense-data "which can with equal truth be described as our sensations or as the qualities of the actual things which we perceive. These qualities are thus relational between the perceiving subject and the perceived things."  It is in this mode that the "world" appears as such, that is, as "a community of actual things," contemporaneous with the subject, which are spatially extended. This sensorially perceived extension arises from "that general scheme of relationships providing the capacity that many objects can be welded into the real unity of one experience."  In other words, the prehensions constituting an actual occasion are "'vectors;' for they feel what is there and transform it into what is here."  Perception of spatial extension, including the appearance of a world as being "external" to consciousness, is the realization in sensory terms of the intrinsic subject-object character of all prehension. But this perceived extensiveness presents a world of separable content, for "in so far as concerns their disclosure by presentational immediacy, actual entities in the contemporary universe are causally independent of each other." 
The world of duality is beginning to emerge, but not quite, for the third aspect of presentational immediacy -- and this also applies to causal efficacy itself -- is its infallibility: "Direct experience is infallible. What you have experienced, you have experienced."  There is no distinction here of true and deluded or illusory perception,  there is simply perception as an ultimate fact, for error arises only in the mixed mode of perception, symbolic reference.
Symbolic reference is the normal perceptual experience of human beings. In it the mode of presentational immediacy, which in itself is little more than a "barren esthetic display," is now reassociated with perception as causal efficacy. The result is the transformation of bare immediacy into a world of meaning, containing emotions, motivations, evaluations, language, art -- as consciousness is now free to refer one component of experience to another. Thus the images of presented immediacy are used to link the "heritage from the past," the objective sources of the concrescing actual occasion, to the possible future as the occasion in turn becomes objectivity for a new occasion. Experience via symbolic reference can be delusive, for "feeling associates regions in the presented locus with inheritances from the past, which in fact have not been thus transmitted into the present regions."  This capacity for error is at times unfortunate in its consequences but is, from Whitehead's perspective, the
source of evolutionary progress in that it testifies to a growing imaginative freedom.  Consciousness makes its gains by its gradually attained freedom from immediate perception, which it is now more and more able to manipulate and modify.
From another -- Buddhist -- angle, symbolic reference is precisely the source of the problem of suffering, for now the consciously dichotomized world has fully emerged. Let us consider Candrakiirti's analysis of the genesis of suffering.  The starting point is "[conceptual] apprehension of an object" (vastuna upalambha), that is, an object per se and detached from its subject as well as from "other" objects. This results in "[verbal-conceptual] proliferation" (prapa~nca) which proliferates the whole "net of fabrication" (kalpanaajaala), which consists of endless discriminations (vikalpa): knowing and known, speech and speaker, actor and act, man and woman, success and failure, happiness and misery, fame and infamy, praise and blame, etc. Based upon these discriminations is the ego (aha^mmama iti) whose addiction (abhinive`sa) they are. This addiction forms the dependency (upaadaana) which is the cause of suffering. Dependency is traditionally analyzed as consisting of: (1) objects of desire (kaama), (2) ethico-religious vows (`siilavrata), (3) views (d.r.s.ti), and (4) assertion of an [essential] self (aatmavaada). These together constitute the ongoing source of suffering in human experience, and it can be alleviated radically only by dissolving the basis for dependency or addiction, namely, the discriminations growing out of conceptual apprehension.
Such apprehension is from Whitehead's point of view the basis of symbolic reference and as such is a manifestation of the creative advance of consciousness, albeit an advance marred by repeated disaster. For Candrakiirti and, apparently, Naagaarjuna, it is the repeated disaster which receives all of the attention.
According to Whitehead, the danger inherent in the emergence of symbolic reference is that it has the tendency to degenerate into mere reflex action: normal human perception via symbolic reference turns to some degree from the conscious linking of presented immediacy with causal efficacy to a semiconscious, reactive linking of the two. The actual effective meaning of what is symbolically perceived is eliminated:
Sometimes there does intervene some effective reference to the meaning of the symbol. But this meaning is not recalled with the particularity and definiteness which would yield any rational enlightenment as to the specific action required to secure the final end. The meaning is vague but insistent. Its insistence plays the part of hypnotizing the individual to complete the specific action associated with the symbol. 
Thus when a car horn sounds, my symbolically referred perception projects upon the bare, presented auditory sense-data my entire causal heritage as it concresces into this actual experience and on toward the future. The spatially localized sound symbolizes its meaning for me, in other words, and I get out of the way. On the other hand reflex action results when I perceive the same sound
as symbol but bypass its actual meaning, that is, the total prehension which constitutes my experience at that moment, and instead I refer it to a stereotyped pattern within my causal heritage. The result is a reflex response which may be "out of touch" with actuality: the car horn, blocks away, triggers in me an overwhelming fear and I spill my coffee on the cat. The determining factor here may lie in a childhood trauma involving a bad experience with a horn, but the present result is that my experience is dominated by a disproportionate ingression of the old pattern into novel conscious occasions.
The Buddhist would say here that this is just what constitutes the suffering arising from dependency -- the addictive patterns (sa^mskaara in its more negative usage) that constitute a stereotyped apprehension of one's own personality (satkaayad.r.s.ti), which in turn elicits stereotyped affective states (kle`sa), which then perpetuate the type of human action that makes up the person's sa.msaaric existence.  For the Buddhist, of course, this situation is not merely an occasional relapse into the automaticity of reflex action (as Whitehead speaks of it) but is rather a fundamental condition -- that is, the underlying addiction or dependency itself -- which obstructs  enlightened knowing and affects all experience with suffering.
There is a difference as I see it between Praasa^ngika Maadhyamika and the Perfection of Insight on this point. Candrakiirti apparently finds the problem of suffering to be inextricably related to the basic mechanism of symbolic reference, namely, conceptual apprehension (upalambha). Hence, full enlightenment or complete nirvaa.na  necessarily requires the elimination of conceptuality. The Perfection of Insight, emphasizing the essential identity of unattached knowing or enlightenment with all things and conditions, allows for the two modes to coexist, in a sense. 
If even discrimination and delusion are ultimately enlightenment, I see no reason why constructive metaphysics need be eliminated from the unattached consciousness of a bodhisattva. I think this is all the more true of a metaphysic such as Whitehead's which, as I have suggested, can be seen to rest on the nondualistic premise that concrete reality is simply a process of knowing (concrescing prehension) -- attached to itself as its own objective causal past, and unattached, as a process of ever-novel self-creation. In other words, I think that Process Philosophy provides a coherent possible ontological explanation for the modes of knowing and the two-truths doctrine of Praj~naa Buddhism. At the same time I would agree with Praj~naa Buddhism that there is no way to consciously experience reality in the unattached mode by means of conceptual understanding and interpretation; for the objective nature of conceptual thought (as apart from the process of thinking itself), that is, the nature of that-which-is-understood, is attached knowing.
1. Usually rendered "Perfection of Wisdom." but an important nuance of penetration is brought out by the word "insight."
2. This is a debatable entity, but I feel it is useful. It is meant particularly to exclude the Yogaacaara school and the school of Dignaaga.
3. The use of verbal paradox as a means of demoralizing conceptual dependency on the part of the listener. The Naagaarjunian dialectic method accomplishes the same thing through the use of logical argumentation.
4. Alfred North Whitehead, Process and Reality (New York: MacMillan, 1927), p. 4, hereafter cited as PR.
5. PR. p. 6.
6. PR. p. 67.
7. PR. p. 7.
8. PR, p. 8.
9. A.s.tasaahasrikaa Praj~naapaaramitaa, ed. P. L. Vaidya (Darbhanga: Mithila Institute, 1960): hereafter cited as AP. Trans. Edward Conze as The Perfection of Wisdom in Eight Thousand Lines (Bolinas, Ca.: Four Seasons Foundation, 1973). Translations hereafter are my own, based upon Conze's. Citations are given for the pagination of the Sanskrit text as given by Conze in brackets and in the margin in Vaidya's edition.
10. Madhyamakakaarikaas (hereafter cited as MK) 24.8-10. Sanskrit text edited by Louis de La Vallee Poussin, Muulamadhyamakakaarikaas (Maadhyamikasuutras) de Naagaarjuna, avec la Prasannapadaa, commentaire de Candrakiirti (St. Petersburg, 1913).
11. MK 24.20 ff.
12. MK 4.14.
13. MK 18.4f.
15. MK 22.11. Thus Naagaarjuna can refer even to valid expressions (yaa yojyate) of Buddhist doctrine as "fabrication" (kalpanaa) endorsed by Buddhas, Pratyekabuddhas, and `Sraavaka (arhats) alike. MK 17.13ff.
16. In his Vigrahavyaavartanii, Naagaarjuna subjects the notion of pramaa.na to the dialectic refutation without explicit discussion of its role in transactional truth, although in verse 6 the four pramaa.nas of perception, inference, scripture, and analogy are mentioned. See Frederick J. Streng, Emptiness: A Study in Religious Meaning (Nashville, Tenn.: Abingdon Press, 1967), pp. 222ff.
17. Ratnaavali 2.35. Naavisa^mvaadavat satya^m [sattvaad] udgatam arthata.h/ paraikaantahita^m satyam ahitatvaan m.r.setarat// reading sems dpas bsgyur ba don du min with the Peking edition of the Tibetan for the second quarter-stanza (vol. 129, p. 176 ^ne 135a). Sanskrit text in P. L. Vaidya. ed., Madhyamaka`saastra of Naagaarjuna (Darbhanga: Mithila Institute, 1960), p. 303.
18. The sources drawn upon here for Candrakiirti's thought are his commentary on the Madhyamakakaarikaas, the Prasannapadaa (see footnote 10), and his Madhyamakaavataara (hereafter cited as MA), available in Tibetan as edited by Louis de la Vallee Poussin, Bibliotheca Buddhica, vol. 9 (St. Petersburg, 1912). A partial translation by de la Vallee Poussin is to be found in Le Museon, vols. 8 (1907), 11 (1910), and 12 (1911).
19. MA, pp. 102f. In translations from the MA, the presumed original Sanskrit terms are given where the correspondences with the Tibetan are reasonably clear.
20. MA, pp. 104f.
21. MA, p. 105.
22. Prasannapadaa, pp. 68 f.
23. MA, p. 109.
24. Prasannapadaa, p. 493.
25. MA, pp. 107f.
26. MA, p. 111: de kho na ~nid bsam pa la 'phags pa rnams kho no tshad ma yin.
27. MA, pp. 112f.
28. Cf. Prasannapadaa, p. 57.
29. Prasannapadaa. p. 75. Here Candrakiirti defines the pramaa.nas of transactional truth to be the three mentioned earlier plus upamaana, analogy. It should be noted that for Candrakiirti direct
perception, pratyak.sa, is not divided into real and illusory perception -- it is simply perception of whatever appears:
Therefore in the world whether it is [called] a definable object (lak.sya), unique particular (svalak.sa.na), or general characteristic (saamaanyalak.sa.na) -- all of it is evident (aparok.sa) because of its being directly apprehended; hence perception (pratyak.sa) is determined by its object (vi.saya) together with cognition (j~naana). Although a double moon and other [illusions] are not perception in relation to the cognition of one free from ophthalmia, they are indeed perception in relation to one having ophthalmia.
30. Prasannapadaa, p. 57.
31. Ratnaavalii 1.60.
32. I leave aside consideration here of the other school of Maadhyamika, the Svaatantrika. Their foremost representative, Bhaavaviveka, was vigorously criticized by Candrakiirti in his Prasannapadaa (chapter 1) for advocating independent logical arguments which were in accord with ultimate truth, rather than simply allowing opponents' arguments to annihilate themselves. See Y. Kajiyama, "Bhaavaviveka and the Praasa^ngika School," in Nava-Nalanda-Mahaavihaara Research Publication, vol. 1 (Nalanda, 1957), pp. 289-331.
33. AP, p. 305.
34. AP, p. 281.
35. AP, p. 274.
36. AP, p. 177.
37. AP, p. 492.
38. AP, p. 15.
39. AP, p. 190.
40. AP, p. 162.
41. AP, p. 475.
42. AP, p. 356.
43. AP, p. 483; compare also p. 358.
44. AP, p. 347.
45. AP, p. 200.
46. AP, p. 30.
47. AP, p. 219.
48. AP, p. 13 (condensed).
49. AP, pp. 34f.
50. AP, pp. 37f.
51. AP, p. 38.
52. AP, pp. 40f; compare MK 25.24.
53. AP, p. 177.
54. AP, p. 271.
55. AP, pp. 350f.
56. AP, p. 46.
57. AP, p. 175.
58. AP, pp. 175f; compare pp. 525f.
59. Conversely, it might be said that connectedness and lack of tranquility are aspects of the attached mode of knowing as well as of the world as conceptually fabricated: subjectively connectedness would mean dependency (upaadaana), while objectively it would mean dependent origination (pratiityasamutpaada); subjectively lack of tranquility would mean suffering (du.hkha) and objectively, perhaps, impermanence (anityataa).
60. AP, 294f; compare p. 275; note also p. 206: "This is the perfection of non-attachment (asa^nga) because all dharmas are without attachment."
61. AP, pp. 205f. All dharmas are like space -- empty; on the other hand, suffering, caused by attachment and perpetuated by the formations (sa^mskaara), pervades all dharmas -- that is, "everything is suffering." This is a hyperparadoxic variation on the basic pattern here.
62. AP, pp. 257, 259.
63. AP, p. 196.
64. AP, p. 197.
65. AP, p. 301.
66. AP, pp. 476f. In this same vein it is said that each of the five bundles is itself both empty and the boundless real nature of all dharmas: a notion which already points to the Avata^msaka doctrine of the interpenetration of all things (AP, pp. 478f.).
67. PR, p. 254.
68. It could equally well be said that the subject is only constituted by (or as) the perceptions of the objects.
69. Alfred North Whitehead, Symbolism: Its Meaning and Effect (New York: G. P. Putnam's Sons, 1959), p. 9; hereafter cited as Symbolism.
70. For example, PR, p. 35.
71. Taking the Buddhist position I would include "mental" perceptions, that is, memories, images, thought patterns, etc. -- as all of these are presentations for contemplative awareness. Phenomenologically considered these would all show the same spatial extension that is so important a component of Whitehead's analysis of presentational immediacy in general.
72. Symbolism, pp. 21 f.
73. PR, p. 105.
74. PR, p. 133.
75. PR, p. 188.
76. Symbolism, p. 6.
77. Symbolism, p. 24; PR, p. 99.
78. PR, p. 274.
79. Symbolism, pp. 19, 59.
80. Prasannapadaa, pp. 350f., commenting on MK 18.4ff.
81. Symbolism, pp. 73f.
82. Prasannapadaa, pp. 350f.
83. Here I am thinking of the two aavara.na or obstructions, kle`saavara.na (the obstruction constituted by addictive greed, anger, and delusion) and j~neyaavara.na (cognitive obstruction).
84. He remarks at MA, 108f, that conventional truth, "because of the activity of the ignorance characterized by the cognitive obstruction alone (and free of kle`saavara.na), appears to the Aryas [who are within] the realm of appearance (aabhaasagocara)" -- but the full enlightenment of the buddhas involves the elimination of the cognitive obstruction and hence conventionality does not appear to them.
85. Compare, note 42, herein, on the dual modality of the bodhisattva's knowing.