Maritain: Definition of Philosophy (Conclusion 1)

Continuing a series of posts that are really nothing more than notes for myself concerning stuff that I'm reading:

Philosophy is not a "wisdom" of conduct or practical life that consists in acting well. It is a wisdom whose nature consists essentially in knowing.

How? Knowing in the fullest and strictest sense of the term, that is to say, with certainty, and in being able to state why a thing is what it is and cannot be otherwise, knowing by causes. The search for causes is indeed the chief business of philosophers, and the knowledge with which they are concerned is not a merely probable knowledge, such as orators impart by their speeches, but a knowledge which compels the assent of the intellect. ...

Knowing by what medium, by what light? Knowing by reason, by what is called the natural light of the human intellect. ... That is to say, the rule of philosophy, its criterion of truth, is the evidence of its object. ...

Knowing what? ... Philosophy ... is concerned with everything, is a universal science. ...

Conclusion I.-Philosophy is the science which by the natural light of reason studies the first causes or highest principles of all things - is, in other words, the science of things in their first causes, in so far as these belong to the natural order (Introduction to Philosophy, pp. 64-69 passim).

Philosophy is limited in the certainty that it provides only to the extent that it deals with questions that are not strictly within its purview, or which have to do with cases for which only probable answers are possible - e.g., application of ethical standards to particular cases (ibid., p. 70).