The subject of the Posterior Analytics is epistêmê.
This is one of several Greek words that can reasonably be translated “knowledge”, but Aristotle is concerned only with knowledge of a certain type (as will be explained below).
There is a long tradition of translating epistêmê in this technical sense as science, and I shall follow that tradition here.
However, readers should not be misled by the use of that word.
In particular, Aristotle’s theory of science cannot be considered a counterpart to modern philosophy of science, at least not without substantial qualifications.
We have scientific knowledge, according to Aristotle, when we know:
– the cause why the thing is, that it is the cause of this, and that this cannot be otherwise. (Posterior Analytics I.2)
This implies two strong conditions on what can be the object of scientific knowledge:
– Only what is necessarily the case can be known scientifically
– Scientific knowledge is knowledge of causes
He then proceeds to consider what science so defined will consist in, beginning with the observation that at any rate one form of science consists in the possession of a demonstration (apodeixis), which he defines as a “scientific deduction”:
– by “scientific” (epistêmonikon), I mean that in virtue of possessing it, we have knowledge.
The remainder of Posterior Analytics I is largely concerned with two tasks:
– spelling out the nature of demonstration and demonstrative science and
– answering an important challenge to its very possibility.
Aristotle first tells us that a demonstration is a deduction in which the premises are:
– primary (prota)
– immediate (amesa, “without a middle”)
– better known or more familiar (gnôrimôtera) than the conclusion
– prior to the conclusion
– causes (aitia) of the conclusion
The interpretation of all these conditions except the first has been the subject of much controversy.
– Aristotle clearly thinks that science is knowledge of causes and that in a demonstration, knowledge of the premises is what brings about knowledge of the conclusion.
– The fourth condition shows that the knower of a demonstration must be in some better epistemic condition towards them, and so modern interpreters often suppose that Aristotle has defined a kind of epistemic justification here.
However, as noted above, Aristotle is defining a special variety of knowledge.
Comparisons with discussions of justification in modern epistemology may therefore be misleading.
– The same can be said of the terms “primary”, “immediate” and “better known”.
Modern interpreters sometimes take “immediate” to mean “self-evident”;
Aristotle does say that an immediate proposition is one “to which no other is prior”, but (as I suggest in the next section) the notion of priority involved is likely a notion of logical priority that it is hard to detach from Aristotle’s own logical theories.
“Better known” has sometimes been interpreted simply as “previously known to the knower of the demonstration” (i.e., already known in advance of the demonstration).
However, Aristotle explicitly distinguishes between what is “better known for us” with what is “better known in itself” or “in nature” and says that he means the latter in his definition.
In fact, he says that the process of acquiring scientific knowledge is a process of changing what is better known “for us”, until we arrive at that condition in which what is better known in itself is also better known for us.