Brightman's Platform of Personalistic Idealism

I am not endorsing this: I note it as an interesting attempt in defining what idealism means:

1. The universe is completely mental in nature.
2. Every mental existent is either a self, or else a part, aspect, phase, or process of a self. The term "person" is used for selves capable of reasoning and ideal valuations.
3. The physical universe may be regarded as the direct experiencing and willing of one cosmic person, or as a system of infra-human selves, or as a system of ideas in the minds of finite persons.
4. The total universe is a system of selves and persons, who may be regarded either as members of one all-inclusive person who individuates them by the diversity of his purposing or as a society of many selves related by common purposes.
5. Every self directly experiences itself.
6. The self knows some other selves indirectly, by inference.
7. Any metaphysical theory (except materialism which denies facts of direct experience) about the quality of reality or the number of ultimately distinct beings is compatible with all scientific observations and with scientific laws conceived either (a) as generalizations of observed sequences or (b) as statistical formulations of average behavior. But philosophy is dependent upon the facts revealed by the sciences for its conception not only of the structure of the universe, but also of its values and purposes.
8. Esthetics and ethics are based on psychological doctrines concerning the valuing consciousness, but go beyond descriptive psychology both in their normative aspects and in their metaphysical implication of beauty and goodness in the universe.
9. Similarly, the science of religion is primarily a psychological and historical discipline; but the object of the religious consciousness, God, may be identified with a metaphysical object -- the cosmic person.

"The Definition of Idealism," The Journal of Philosophy, 1933