While Kant's term "intellectual intuition" is thrown around rather casually in post-Kantian philosophy, the usage rarely conforms to Kant's meaning. Kant contrasts "intellectual" with "sensible" intuition (Anschauung) on the basis of the active or passive role of the object. Thus, while objects are presented to a (passive) sensible intuition, objects are created by an (active) intellectual intuition. To Kant himself, this meant that only God would have an intellectual intuition. In the history of philosophy, the "active intellect" of Aristotle and Neoplatonism (http://www.friesian.com/hist-1.htm#late) may be the antecedent of the idea of intellectual intuition, though this would tend to blur the difference between the self and God, since it looks like there is only one active intellect -- which was precisely the point for a system of mysticism like Neoplatonism.
Kant, of course, had no interest in mysticism, famously pillorying the Swedish spiritualist, Emanuel Swedenborg ("Dreams of a Visionary, Explained by Dreams of Metaphysics," 1766), but it is important to note what mysticism would be in Kantian philosophy. Any kind of mysticism is going to be a kind of immediate knowledge that is an intuitive understanding, i.e. the opposite of a discursive understanding, where an intuitive understanding is immediate and unarticulated, while a discursive understanding is mediate and articulated. There is going to be no intuitive understanding in Kantian philosophy -- i.e. no understanding that stands on its own as knowledge, an understanding that is a ground for substantive truths. An intuitive understanding which is not knowledge is the common and essential experience of insight which is ordinarily and non-technically called "intuition," e.g. "My intuition is that murder is wrong" (in German, Nelson (http://www.friesian.com/nelson.htm) called it Intuition in contrast to Kantian Anschauung). This kind of "intuition" is not evidentiary, i.e. it doesn't prove anything. In Socratic/Platonic terms, it is only opinion. It can only be justified when analyzed, reduced to discursive understanding, and grounded accordingly [note]. Were ordinary "intuitions" evidentiary, and so items of knowledge (Erkenntnisse, cognitions), then this would be "intuitionism," the theory that knowledge is grounded by such intuitions [note]. The self-evidence of Aristotelian first principles (http://www.friesian.com/founda-1.htm) is a theory of this kind, with the proviso that intuitive self-evidence follows, rather than precedes, discursive understanding. Other forms of intuitionism may claim intuitive understanding prior to discursive, if the latter is considered even possible.
While mysticism is a form of intuitionism, not all intuitionism is mysticism. The difference, again, will be in the objects. Mysticism is intuitive knowledge of transcendent concrete objects, i.e. not the phenomenal or material concrete objects of ordinary perception. The mystic sees things that are not part of ordinary experience. In Kantian terms, transcendent objects cannot be understood because they cannot be consistently articulated. For Kant, a theory of transcendent objects ("dialectic") generates antinomies (http://www.friesian.com/antinom.htm). If a Kantian theory allowed for mystical knowledge, it would have to be unanalyzable, unrenderable into a system of discursive understanding of transcendent objects. This is rather like what many mystics say, since they gain knowledge which is ineffable and inexpressible. On the other hand, mystics also claim to intuitively derive knowledge which is analyzable and expressible, although only intuitively justified, since, for instance, al-Ghazzali (http://www.friesian.com/hist-1.htm#islam) (1059-1111) finds specific justification of Islām and its doctrines through mystical insight.
The intuitive apprehension of abstract objects does not rise to the level of mysticism, since abstract objects do not have independent existence -- except when substantialized in Platonism, a theory rarely followed since. Intuitions of abstract objects concern meaning (http://www.friesian.com/universl.htm), and in general the ordinary sense of "intuition" (Intuition) applies to this. Such intuitions, when analyzed, are the basis of analytic truths, but whether the meanings apply to existence is a separate question (pace St. Anslem and Descartes (http://www.friesian.com/hist-2.htm#descartes)), which requires an evidentiary basis. The mystical claim would have to be that an intuitively apprehended abstract object is also intuitively known to apply to existence, in a way, analyzable (as in Anselm's "ontological argument") or unanalyzable, that transcends ordinary perception and experience.
An important distinction in mystical claims will be between objects which are independent and which are identical to the subject of mystical knowledge. This itself is an analyzable characteristic of mystical intuition. In monotheistic religions, God will tend to be seen as independent. This was not an open question, and the Christian mystic always ran the risk that contrary truths learned through mystical intuition might conflict with Orthodoxy -- but the Catholic Church never denied that such an avenue of knowledge existed, as with St. Teresa of Įvila (1515-1582). Other mystics, however, paid the price of their experiences at the stake. In Judaism and Islām, with looser institutional authority over doctrine, the drift of claims towards extinction of self and identity with God is conspicious. Some efforts were made in Islām to suppress this, like the execution of al-H.allāj (in 922), but the precedent was powerful. An artifact of this in Judaism remained with the philosopher Spinoza (http://www.friesian.com/spinoza.htm), whose sense of identity with God is crystal clear, but who cannot properly be considered a mystic, since his God is not transcendent, but immanent, identical with all the objects of perception, and who does not claim intuitive knowledge beyond the minimal Aristotelian claims about first principles. Nevertheless, Spinoza retains a strong mystical affect, the "intellectual love of God," which helps explain the meaning to him of a system that otherwise is rationalistic and seems devoid of religious appeal.
The distinction between independent and identical objects can be seen to overlap Kant's between intellectual and sensible intuition. Only a sensible intuition could relate one to an independent transcendent object, since such a thing clearly cannot be created by one's knowing it. However, if the mystic is identical to the transcendent object, this could allow for an intellectual intuition, depending on the metaphysics of the object. It is possible for God's existence to be presented to him passively, in which case he would have sensible knowledge of himself; or, God may actually create his own existence, like that of anything else, merely by knowing it. This fits Spinoza's priniciple of a substance, namely God (Spinoza's only substance), being self-caused. There, if the mystic is identical to God, who also creates everything else through intellectual intuition, all mystical knowledge will be of the nature of an intellectual intuition.
This is even simpler in Buddhism, where there are no substances and, at least in some forms of Buddhist philosophy (http://www.friesian.com/buddhism.htm#basic) (e.g. Yogacara), all things are clearly created by Mind. In Pure Land (http://www.friesian.com/six.htm#japan) Buddhism, an important meditative practice is the visualization of the Pure Land of the Buddha Amitabha. It is always possible to interpret this as unrelated to the independent, or even real, existence of the Pure Land, but the metaphysics clearly allows that the Pure Land is actually created by the act of visualization, since all things are Mind dependent. This would be an intellectual intuition in a strong Kantian sense, and a form of mysticism, with the transcendence of the Pure Land, in which the identity with the mystical object is fascilitated by the absence of any substantial independence of things whatsoever. Similarly, the Tibetan "Book of the Dead" urges the deceased to realize that the visions of the hereafter are not independent but created by their own Mind. Thus lies the path to Enlightenment and Salvation.
In light of this examination, we should revisit the charge of mysticism (http://www.friesian.com/edwards.htm) against Rudolf Otto (http://www.friesian.com/otto.htm). Since Otto does not claim intuitive knowledge of transcendent objects, he clearly is not a mystic. The natures of transcendent objects, to the extent that they can be theorized at all, are matters of rational Kant-Friesian metaphysics (after the fashion of Kant's "postulates of practical reason," which resolve some antinomies); and Kant-Friesian metaphysics tends to dismiss more substantive doctrine from historic religions (e.g. the Trinity, transsubstantiation, etc.). Otto's famous theory of "numinosity" is about a property, and so an abstraction, whose existence is certified by its presence in the objects of experience, but which in an important way is not a natural property, since it is invisible to science and is unrelated to mundane utility. The numinosity of God is natural to Otto, but his God comes from the Kantian Ideas, besides historic religions, and divine numinosity derives from no more than a phenomenology of such religions.
So is there mysticism? Of course, since there actually are mystics, most of whom are clearly sincere and deeply moved or transformed by their experiences. But there is no philosophical mysticism in the sense that philosophy could, as the Neoplatonists believed, certify, verify, and theorize the results of mystical intuitions. Given a Kantian epistemology and metaphysics, no rational or intelligible system can be built from mystical intuitions, analyzable or unanalyzable. This, however, should be no more than what we would expect given the contradictory claims of mystical or dogmatic authorities in world religions. The antinomical choices between mystical intuitions as intellectual or sensible, of independent or identical objects, of a divine substance (personal or impersonal) or ultimate Emptiness, cannot be resolved on the evidence of mystical knowledge, since the knowledge of different mystics confirms each of these and, as Hume would say, the evidence of one tends to refute the evidence of the other. This in itself is one of the most important features of human existence, since it leaves us without any rational certainty that there are transcendent objects at all. The mystic may just be hallucinating (or lying), whether beholding the Virgin Mary or visualizing the Pure Land. As considered elsewhere (http://www.friesian.com/need.htm), however, this simply leaves us faced with the choices of the right and the good without any confidence in the ulterior considerations of reward and punishment. Behind our veil of ignorance, it is character and benevolence that are proven.
Faith, Works, and Knowledge (http://www.friesian.com/faith.htm)
Analytic and Synthetic: Kant and the Problem of First Principles
Philosophy of Religion (http://www.friesian.com/religion.htm)
History of Philosophy (http://www.friesian.com/history.htm)
Home Page (http://www.friesian.com/#kant)
Problems of justification are covered elsewhere (http://www.friesian.com/founda-2.htm). In Kant's theory, complications arise over Kant's original, "architectonic," conception of intuition (Anschauung) because, as considered in the main essay on Kant, perception itself comes to be seen (in the Transcendental Deduction) as a product of mental activity. If perception is itself active and intellectual, then the simple distinction between sensible and intellectual intuition, or even between intuition and thought, becomes confused. Friesians like Nelson don't deal with his very well and tend to take over Kant's own naive version of the theory.
However, as is examined in detail in The Origin of Value in a Transcendent Function (http://www.friesian.com/origin/) ("Intuition and the Immanent Object (http://www.friesian.com/origin/chap-3.htm#sect-6)), the immediacy of intuition that is lost when we consider perception to be the result of active mental synthesis returns when we realize that this synthesis is an activity that cannot occur in the conscious mind. Perception is spontaneously produced by a preconscious activity; and even if it is governed by Kant's "pure concepts of the understanding" as rules of synthesis, these concepts do not accompany the results as conceptual or semantic content. Perception can occur without being understood, without particular things being seen, or without a particular recognition determined by the percept -- as in the Gestalt tricks where different things (e.g. faces or candlesticks) can be seen in the same shapes. The difference between conceptual meaning and perceptual object must be maintained, even when the empiricist tabula rasa is rejected and mental processes are allowed into the formation of perception. It is thus possible to continue speaking of intuition pretty much as Kant and the Friesian do, even after taking into account the way that the Transcendental Deduction undermines Kant's original view of intuition. There is also the ontological aspect to this, that the phenomenal objects immanent in perception are undecidably (http://www.friesian.com/undecd-1.htm) both real/external and subjective/internal.
In arguments about mathematics and set theory, "intuitionism" tends to mean something else, which can be very confusing. Mathematical intuitionists don't like mathematical or logical constructions that cannot be visualized (hence, "intuited") and so tend to be wary or disapproving of infinities. Such scruples, however, which may be empiricist in origin, seem to have had little effect on the practice of mathematics and, if taken seriously, would make much of modern mathematics, including non-Euclidean geometry (http://www.friesian.com/curved-1.htm), suspect. While Kant might be said to be a kind of intuitionist in this sense, since he thinks that the axioms of geometry and arithmetic are grounded by visualization, there is nothing to prevent the logical extension of mathematics beyond our capacity for visualization, which in fact is what has occurred. While Kant's mathematics is somewhat intuitionistic in the modern mathematical sense, it is not necessarily intuitionistic in the traditional epistemic sense, since our mathematical "intuitions," e.g. "that looks like a triangle," can be wrong. The Kantian mathematical intuition is much more like perception, an empirical intuition, than it is like a true self-justifying, evidentiary intuition -- a Kantian mathematical intuition, like an empirical intuition, can be misunderstood, while the evidentiary intuition of (epistemic) intuitionism is itself a kind of infallible understanding. To prevent confusion, the mathematical sense of "intuition" and "intuitionism" is not used in the text.