The discussion between realism and idealism is fundamentally one about clothes--in what garments shall the spiritual realities that are the real matter of all art be arrayed. Whether it shall be sought for in the aspects of everyday things, or clothed by the artist in the most fit symbols his imagination can conceive. The reality is the same in the best examples of all art, whether real or ideal. It is this inner world of reality, the other side of material things, that art seeks to give expression to in the material terms. The old antagonism between the material and the immaterial, between the flesh and the spirit, has too often in the past led the idealist to neglect the true aspect of things (the material with which his symbols are made), and inclined the realist to give too much emphasis to the purely material aspect of things, to the neglect of the spirit. But the more reasonable modern minds are everywhere seeking to combine these two extremes, seeking the inner realities in the meanest aspect of everyday things, instead of building in the clouds. There is, truly speaking, no antagonism between the realist and the idealist.1
If you don't already own them, you owe it to yourself to pick up a copy of Harold Speed's essential texts on learning to draw and paint. The Practice and Science of Drawing and Oil Painting Materials and Techniques. They offer a wealth of practical information on learning the craft as well as a generous amount of sound artistic theory and philosophy. Along with Robert Henri's The Art Spirit, I would consider them required reading for anyone pursuing art. More from these two in the future.
1 Harold Speed, Oil Painting Materials and Techniques (New York: Dover, 1987) 66