Idealism is ideal lives more frivolously and impudently than a man with no ideal at all.
Idealism is a philosophical school which places emphasis on human consciousness rather than on the world itself.
Idealism is any philosophy which tries to base ideas of reality or truth on an analysis of consciousness.
Idealism is evidenced in the fact that the concept of causality is essential to the possibility of perception. That means that causality (which sits in the understanding rather than in the world) is the condition for the possibility of perception.
Idealism is to be found in action. Man is born a predestined idealist, for he is born to act. To act is to affirm the worth of an end, and to persist in affirming the worth of an end is to make an ideal.
Idealism is incoherent. The external world cannot be the work of our organs, because then our body, as a part of this external world, would be the work of our organs, but then our organs themselves would be the work of our organs!!!!.
Idealism is the idea that the world of spatio-temporal matter we take ourselves to perceive is in fact only the appearance of some ground not revealed by that appearance (but to some extent can be determined by the will).