For Plato, ideas like Beauty, Courage, Love, Justice, and all other metaphysical concepts only have any real basis in capital "T" Truth whenever they are contemplated outside of the senses. As he argued in The Republic, individuals are only able to come to an authentic reality of a concept once they have gone through an extensive process of dialectic, which, for him, was a rigorous examination of one's strongly held beliefs. This examination, which consisted of putting one's perceptions of the world up for question, would only be complete once an individual had reached a point of interrogation at which they no longer found any inherent contradictions between what they believed to be true and the real form of the idea itself. Knowledge arrived at by this method was the purest of all forms, and Plato believed it to reflect the Truth about the reality of the world.

Thus, as a direct answer to your question, Plato would argue that the ideas of Beauty, Courage, and the like are real, but that we can only arrive at an accurate understanding of them at the level of human reason. Plato strongly argued against any attempt to understand the world and form strong opinions of it by reference to the senses alone. He illustrated the point by evoking the imagery of the tree. In the summer time, a person may look at a tree when its flowers are blooming and believe that it is very beautiful. However, in the winter, this same tree, now wet, without its leaves, and morbid, is unappealing, and that same observer may believe that it is no longer beautiful but is rather ugly. But how can a single object be both beautiful and ugly at once? Or, put another way, how can the same object, viewed by the same viewer, possess contradictory elements? For Plato, this was because understanding granted by the senses alone was always bound to lead to inaccuracies.

What was the solution, then? Plato believed true knowledge of a metaphysical idea like Beauty or Courage to only be accessible at the highest levels of individual contemplation. The purest form of an idea, one that had been freed of any internal contradictions (like the tree) of thought, was what Plato called and Idea (with a capital "I"), and it resided in the realm of pure reason alone. The Idea of a metaphysic (say, the Idea of Beauty, the Idea of Courage, etc.) was not the thing as it manifested in any one particular object in nature (i.e., the beauty of a particular tree or the courage of a particular soldier) but rather an abstracted, purified form. This Idea then gave reality to all of the things in the material world that corresponded to it. Thus, the Idea of Courage provided all things in the material world that could be courageous with courage.

Plato explained this apparently difficult philosophical concept quite well in Bbook 6 of The Republic with his metaphor of the Sun....