The works of Aristotle as they have come down to us include what seem to be nearly opposite statements about the knowledge of first principles. Book 1 of the Topics, Aristotle’s treatise on dialectic, says that dialectic, which assumes no pre-existing truth and does not yield certain conclusions, turns out to be the best way to the investigate first principles.
However, striking a much more Platonic note, book 1 of the Metaphysics says that knowledge of first principles or “wisdom” is the most difficult of all, but is also the most exact kind of the knowledge in the strong sense that is often translated as “science”. This is said to include knowledge of goods or ends, along with other sorts of causes. But then again, book 1 of the Nicomachean Ethics insists that ethics and the practical judgment associated with it are necessarily inexact. This latter difference seems to have to do the status of first principles as universals, in contrast to the concern of ethics with particular actions.
While book 1 of the Metaphysics is a beautiful text with many valuable insights, the idea that knowledge of first principles could be what is most exact seems incongruous to me. It seems to assume an unequivocal priority of universals over particulars, whereas I think the overall balance of Aristotle’s work shows a much more even-handed view. The ethics, the dialectic, the biological works all take a more nuanced approach. My favorite part of the diverse collection that is the Metaphysics is the very dialectical part in the middle about substance, potentiality, and actuality. (See also Interpretation; What and Why; First Principles Come Last.)