I. 3. 4-5
(Armstrong Selection and Translation)
(A description of the Platonic method of dialectic, followed by an insistence that it is not a mere science of propositions, but brings the mind into immediate contact with the highest realities.)
What then is dialectic, which the other kinds of men as well as philosophers must be given? It is the science which can speak about everything in a reasoned and orderly way, and say what it is and how it differs from other things and what it has in common with them; in what class each thing is and where it stands in that class, and if it really is what it is, and how many really existing things there are, and again how many non-existing things, different from real beings. It discusses good and not good, and the things that are classed under good and its opposite, and what is the eternal and what not eternal, with certain knowledge about everything and not mere opinion. It stops wandering about the world of sense and settles down in the world of Noûs, and there it occupies itself, casting off falsehood and feeding the soul in what Plato calls ‘the plain of truth’, using his method of division to distinguish the Forms, and to determine the essential nature of each thing, and to find the primary kinds, and weaving together by the intellect all that issues from these primary kinds, till it has traversed the whole intelligible world; then it resolves again the structure of that world into its parts, and comes back to its starting-point, and busies itself no more, but contemplates, having arrived at unity. It leaves what is called logical activity, about premises and syllogisms, to another art, as it might leave knowing how to write. Some of the matter of logic it considers necessary, as a preliminary, but it makes itself the judge of this, as of everything else, and considers some of it useful and some superfluous, and belonging to the discipline which wants it.
But from where does this science derive its principles? Noûs gives clear principles to any soul which can receive them: and then it combines and interweaves and distinguishes their consequences, till it arrives at perfect intelligence. For, Plato says, dialectic is ‘ the purest part of intelligence and wisdom’. So, since it is the most valuable of our mental abilities, it must be concerned with real being and what is most valuable; as wisdom it is concerned with real being, as intelligence with That which is beyond being. But surely philosophy is the most valuable thing? Are dialectic and philosophy the same? It is the valuable part of philosophy. For it must not be thought to be a tool the philosopher uses. It is not just bare theories and rules; it deals with things and has real beings as a kind of material for its activity; it approaches them methodically and possesses real things along with its theories.