Christianity has emphasized the path of Love, while Buddhism has put more emphasis on the path of Reason. But, of course, neither downplays the other (except for certain Christian Protestant strains). The Catholic Catechism, for example, says that "sin is an offense against reason", while the Buddhist should never let Compassion get under the radar.
Some notable names who have taken the path of Reason are the Buddhist Nagarjuna, the Vedantist Shankara, the pagan Plotinus, and the Christian Nicholas of Cusa. And, of course, Wolff, who has, I think, provided the contemporary reader with the most articulate expression of this path, in his two books Pathways Through to Space and The Philosophy of Consciousness Without an Object, both reprinted in a single volume: Experience and Philosophy. Another philosophic overview, not of the path, but of the resulting worldview, can be found in Owen Barfield's What Coleridge Thought.
Both paths have dangers. Love can be misdirected, and reason can go astray, which is to say that both are susceptible to idolatry. For this reason, one might say that the first commandment of the path of Reason is to learn to think with the danger of idolatry in mind. Buddhism has a tool for that, which I will get to shortly. First, though, there is a need to make a distinction within the general category of reason. Unfortunately, different authors have used different words, or the same words in opposite ways. In particular, Cusa distinguished between intellectus and ratio to mean what Coleridge meant by reason and understanding respectively. Hence I will borrow some terminology from Pirsig's Metaphysics of Quality (MoQ -- see his book Lila) and call the first 'dynamic intellect' and the second 'static intellect'. I should mention that the concept of 'dynamic intellect' does not occur in the MoQ, which in my opinion is a major reason that it fails as a metaphysics, but that's another story. Pirsig applied the words to Quality: dynamic quality and static quality, with the idea that dynamic quality is the undefinable creative whatever (force? power?) that leaves in its wake static quality. Hence, I am using the words in the same way: dynamic intellect is creative, while our understanding of the created is static intellect. But they cannot really be divided, in the sense that they are mutually dependent, but that is getting ahead of the story.
The story begins, and never gets past, the intellectual confrontation with mystery. Mystery is that which is real, but can never be captured by static intellect, which is to say, can never be understood. Idolatry and heresy consist largely of replacing the mystery with something understandable (a practice that is not restricted to religious mysteries). But if there is no possibility of understanding, why pursue the matter with intellect? In fact, many mystics, and writers on mysticism, enjoin just that -- better to drop it and take the path of Love, for example. Well, that is an option, no question, and I make no claim that one should pursue it intellectually. But for those who choose to do so...
Goethe said: "One is only truly thinking when that which one thinks cannot be thought through", and that's the kind of thinking we are talking about. The path of Reason is one of purifying one's intellect. Hence, both Plotinus and Wolff recommend as therapy the study of philosophy and mathematics. It is not that one will find in either discipline the answers to mysteries, but that both serve as discipline in purifying one's intellect. One thing to note in philosophy, though, is that certain issues constantly recur without resolution (which is to say that resolving them leads to bad philosophy): free will and determinism, the one and the many, being and becoming, and so on. The path of Reason, however, has a tool that consists of holding these oppositions in tension without resolving them. It has various names. Cusa called it the 'coincidence of opposites', which I think as a name does not work well. Coleridge called it 'polar logic'. Nishida Kitaro called it the logic of contradictory identity, along with various variations like 'self-contradictory identity'. I shall adopt this but with one change, thanks to a remark of Barfield's in his discussion of Coleridge, and that is to substitute the word 'contrafactory' for 'contradictory'. Hence: the logic of contrafactory identity, or LCI. The reason for the substitution is that the logic does not just apply to a situation where two words are needed that contradict each other, but that in emphasizing one word, the need for the other is made. This situation has been admirably expressed by Wolff:
While in the State [of High Indifference, as he called it], I was particularly impressed with the fact that the logical principle of contradiction had no relevancy. It would not be correct to say that this principle was violated, but rather, that it had no application. For to isolate any phase of the State was to be immediately aware of the opposite phase as the necessary complementary part of the first. Thus the attempt of self-conscious thought to isolate anything resulted in the immediate initiation of a sort of flow in the very essence of consciousness itself, so that the nascent isolation was transformed into its opposite as co-partner in a timeless reality....It seemed to be the real underlying fact of all consciousness of all creatures. [Franklin Merrell-Wolff, Experience and Philosophy, p.286]
It is that "sort of flow" and "transform[ing] into its opposite" that I mean to get at with the word 'contrafactory'. What this says about consciousness in particular is also to be looked into, briefly below, but I hope in more detail in another post.
Nishida's logic of contradictory identity was a contemporary version of something that has long existed in Buddhist philosophy, stemming from Nagarjuna, and codified into what is called the tetralemma. It is invoked when one is confronted with one of these perennial philosophical puzzles, like "does the self exist". What the Buddhist logician does is refute the following four possibilities: (1) the self exists, (2) the self does not exist, (3) the self both exists and does not exist, and (4) the self neither exists nor does not exist.
Now the actual refutations are carried out using familiar Aristotelian logic: one assumes (1) and deduces a contradiction, then one assumes (2) which also produces a contradiction. Now at this point, I believe I am veering off from the original Nagarjunic approach (though perhaps not Nishida's -- I'm just not sure). For as far as I can tell, (3) is considered to be refuted simply because it violates the law of contradiction, and (4) because it violates the law of the excluded middle. One reason for veering off is that nowadays we have quantum mechanics to consider: is an object in a superposition of states an existing somewhat that violates the principle of contradiction and/or the law of the excluded middle? I think there is an interesting question here, but tangential. But sticking to questions like the existence of the self, I see (3) and (4) as having more to them. Now (3) may just be an acknowledgment that we cannot think what it means to both exist and not exist, but (4) I see as a commandment: thou shalt not stop asking the question. This, by the way, is in defiance of the pragmatist, who says: it is a question that is not worth pursuing. Or more accurately, it is in defiance of the nominalist pragmatist, who believes that words are simply human inventions, and if there are areas where the application of a particular word (like 'self') gets problematic, just back off from those areas. In contrast, the path of Reason says "don't stop the question", because the mystery is real and can't be ignored -- in this case, without the word 'self' how can one say that it must -- in some mysterious sense -- die, as most mystics are wont to say?
There is more to say, of course, but for now I want to conclude by referring back to the Wolff quote, in which he is talking about noetic experience while in a mystical state of consciousness. It ends with "It [the flow from one state to its opposite] seemed to be the real underlying fact of all consciousness of all creatures." What this indicates to me -- and I'll grant that I am speculating here -- is that the LCI is not just a way for fallible human intellects to confront mystery, but is "in fact" what consciousness is. (The scare quotes are -- as usual -- needed because this is of course not some fact lying around to be observed.) That is, what Wolff seems to be saying is that consciousness "works" by contrafactory identity. And it is possible that one can say the same about dynamic/static intellect.