Spinoza identifies three kinds of “knowledge”.
“From what has been said above, it is clear that we perceive many things and form universal notions:”
“I. from singular things which have been represented to us through the senses in a way that is mutilated, confused, and without order for the intellect…; for that reason I have been accustomed to call such perceptions knowledge from random experience;”
“II. from signs, e.g., from the fact that, having heard or read certain words, we recollect things, and form certain ideas of them, which are like them, and through which we imagine the things…. These two ways of regarding things I shall henceforth call knowledge of the first kind, opinion or imagination.”
“III. Finally, from the fact that we have common notions and adequate ideas of the properties of things…. This I shall call reason and the second kind of knowledge.”
“[IV.] In addition to these two kinds of knowledge, there is another, third kind, which we shall call intuitive knowledge. And this kind of knowing proceeds from an adequate idea of the formal essence of certain attributes of God to the adequate knowledge of the… essence of things” (Ethics, book 2, proposition 40, scholium 2, Collected Works vol. 1, Curley trans., pp. 477-478).
The first kind is the source of the confusion addressed in the last post. It elaborates on Plato’s account of “mere opinion”. An important detail is Spinoza’s explicit reference to the fact that inadequate “universal” notions are commonly formed based on inadequate ideas from perception and imagination. Formal logic can then be mechanically applied to these inadequate universals, yielding conclusions that are formally logically sound but deeply wrong materially or content-wise when applied to the real world. We’ve all seen this happen.
The second kind, which he calls “reason”, is thus distinguished not by its use of logic but by the kind of contents it addresses: common notions and adequate ideas. For Spinoza, “reasoning” that takes mere images and opinions as unproblematic sources of truth does not deserve the name of Reason.
“Common notions” is Spinoza’s preferred term for principles that are recognized by all humans and are “equally present in the part and the whole”. What exactly these are intended to include is somewhat obscure. His main example of common notions involves simple mathematical properties of bodies, which are “common” due to the presumed objectivity of mathematics, rather than any sort of intersubjectivity or mutual recognition.
“Adequacy” of ideas is an entirely internal criterion — basically a kind of coherence of meaning, rather than a correspondence with something external that is presumed to be independently known. Ideas for Spinoza are things we affirm or deny, so they have internal complexity. Adequacy of ideas seems to be entirely independent of his criteria for common notions, which is good because I worry about the narrowness of the latter.
I read the third kind — “intuition” — as presupposing and building on the discipline of the second. It is not a free-for-all. This is a “cumulative” rather than “originary” intuition. What other authors claim as originary intuition (alleged “self-evident truths” coming from nowhere) would for Spinoza be mere opinion or imagination.
He says that the first kind of knowledge is the only source of falsity, which implies that the results of the second and third kind are always true. While it is clear that the first kind is a source of falsity, to say that reason and “intuition” yield only truth sets a very high standard indeed. He does not seem to acknowledge the difficulty of knowing there is no admixture of the highly fallible first kind in what we may take to be the infallible second or third kind, or in general the difficulty of practically achieving the extremely high standards he sets for the second and third kind.
This whole discussion proceeds very hastily. There is a bit more than I have quoted, but only a bit. His account of the first kind of knowledge and its weaknesses is relatively more extended, and quite vivid and insightful. But the account of the second kind is very sketchy, and the account of the third kind even more so.
Perhaps we are intended to see the whole text of the Ethics as an illustration of how the second and third kind work. But if it purely embodies the infallible second and third kinds of knowledge, then it would seem that all serious philosophers ought to unequivocally endorse all its arguments, or else they won’t qualify as serious. Strictly speaking, does Spinoza’s standpoint even allow him to acknowledge another philosopher as serious who does not endorse all his arguments? Honestly I did not expect to write the previous sentence.
While Spinoza does not seem to me to be what Kant would call a dogmatist in the sense of taking objects for granted, there is a sense in which he does seem to say, “here is my system, take it or leave it”. I’m still not sure what I think of Hegel’s claim that no finite presentation can ever be truly final, but relatively speaking I’m more comfortable with that. I want to say it is actually a principle of charitable reading to at least in some measure tolerate excessive claims a work may make on its own behalf, and focus instead on understanding the content.