These dialogues seldom end with positive conclusions, although a premature version of the theory of forms is always presumed by Plato, as well as a moral standard that defines human good as wisdom and virtue (even if those things are hard to define), rather than wealth or status. The middle dialogues are centered on the Republic; now, Plato's own philosophy begins to overcome the elenchus and Plato's views are put forward in favor of Socrates' sometimes indecisive method. The later dialogues are extremely difficult and controversial from a scholarly perspective--they contain Plato's more complex philosophical and logical views, and there is great controversy surrounding what "trends" and themes could be said to identify this period.
Characteristically Platonic philosophy begins to appear, then, in the middle dialogues. What are the important elements of this philosophy? The middle dialogues are dominated by the theory of the Forms. This is a theory that Plato developed from certain seldom-stated assumptions that Socrates held. Socrates' view was that the reason he and his interlocutors failed to find definitions for things was that they were stuck in case-based, specific examples. Does bravery mean fighting against a person stronger than yourself, or does it mean having the courage to back down from the fight and accept the insults of cowardice that come with that; does it mean having the determination to turn your father in for murder, or bravely facing him about it, because he's your father? Such examples are bound to contradict themselves. Socrates felt that there was one bravery that was common to all these braveries, and is what makes them "brave." Plato sculpted this idea into his theory of Forms. The Forms are, basically, essences--they are that which truly defines a thing. By the time of the Republic, Plato had come around to the view that everything had Forms--not just virtues, but tangible things like beds, chairs, etc.
