This conception of the position of poetry in the body of human knowledge may be found, however, throughout the Renaissance. Thus, Robortelli, in his commentary on Aristotle's _Poetics_ (1548), gives the usual scholastic distinctions between the various forms of the written or spoken word (_oratio_): the demonstrative, which deals with the true; the dialectic, which deals with the probable; the rhetorical, with the persuasive; and the poetic, with the false or fabulous.[40] By the term "false" or "fabulous" is meant merely that the subject of poetry is not actual fact, but that it deals with things as they ought to be, rather than as they are. Varchi, in his public lectures on poetry (1553), divides philosophy into two forms, real and rational. Real philosophy deals with things, and includes metaphysics, ethics, physics, geometry, and the like; while rational philosophy, which includes logic, dialectic, rhetoric, history, poetry, and grammar, deals not with things, but with words, and is not philosophy proper, but the instrument of philosophy. Poetry is therefore, strictly speaking, neither an art nor a science, but an instrument or faculty; and it is only an art in the sense that it has been reduced to rules and precepts. It is, in fact, a form of logic, and no man, according to Varchi, can be a poet unless he is a logician; the better logician he is, the better poet he will be. Logic and poetry differ, however, in their matter and their instruments; for the subject of logic is truth, arrived at by means of the demonstrative syllogism, while the subject of poetry is fiction or invention, arrived at by means of that form of the syllogism known as the example. Here the enthymeme, or example, which Aristotle has made the instrument of rhetoric, becomes the instrument of poetry.