Idealism and Materialism (Dan Lusthaus)
This is extracted from an online essay What Is and Isn't Yogācāra , Dan Lusthaus, on a site which goes offline regularly. This excerpt is published for private discussion purposes only. (Yogācāra, 'mind-only Buddhism', is sometimes equated with philosophical idealism, the point of Lusthaus' original essay is to disambiguate them.)
The term "Idealism" came into vogue roughly during the time of Kant (though it was used earlier by others, such as Leibniz) to label one of two trends that had emerged in reaction to Cartesian philosophy. Descartes had argued that there were two basic yet separate substances in the universe: Extension (the material world of things in space) and Thought (the world of mind and ideas). Subsequently opposing camps took one or the other substance as their metaphysical foundation, treating it as the primary substance while reducing the remaining substance to derivative status. Materialists argued that only matter was ultimately real, so that thought and consciousness derived from physical entities (chemistry, brain states, etc.). Idealists countered that the mind and its ideas were ultimately real, and that the physical world derived from mind (e.g., the mind of God, Berkeley's esse est percipi, or from ideal prototypes, etc.). Materialists gravitated toward mechanical, physical explanations for why and how things existed, while Idealists tended to look for purposes - moral as well as rational - to explain existence. Idealism meant "idea-ism," frequently in the sense Plato's notion of "ideas" (eidos) was understood at the time, namely ideal types that transcended the physical, sensory world and provided the form (eidos) that gave matter meaning and purpose. As materialism, buttressed by advances in materialistic science, gained wider acceptance, those inclined toward spiritual and theological aims turned increasingly toward idealism as a countermeasure. Before long there were many types of materialism and idealism.
Idealism, in its broadest sense, came to encompass everything that was not materialism, which included so many different types of positions that the term lost any hope of univocality. Most forms of theistic and theological thought were, by this definition, types of idealism, even if they accepted matter as real, since they also asserted something as more real than matter, either as the creator of matter (in monotheism) or as the reality behind matter (in pantheism). Extreme empiricists who only accepted their own experience and sensations as real were also idealists. Thus the term "idealism" united monotheists, pantheists and atheists. At one extreme were various forms of metaphysical idealism which posited a mind (or minds) as the only ultimate reality. The physical world was either an unreal illusion or not as real as the mind that created it. To avoid solipsism (which is a subjectivized version of metaphysical idealism) metaphysical idealists posited an overarching mind that envisions and creates the universe.
A more limited type of idealism is epistemological idealism, which argues that since knowledge of the world only exists in the mental realm, we cannot know actual physical objects as they truly are, but only as they appear in our mental representations of them. Epistemological idealists could be ontological materialists, accepting that matter exists substantially; they could even accept that mental states derived at least in part from material processes. What they denied was that matter could be known in itself directly, without the mediation of mental representations. Though unknowable in itself, matter's existence and properties could be known through inference based on certain consistencies in the way material things are represented in perception.
Transcendental idealism contends that not only matter but also the self remains transcendental in an act of cognition. Kant and Husserl, who were both transcendental idealists, defined "transcendental" as "that which constitutes experience but is not itself given in experience." An example would be the eye, which is the condition for seeing even though the eye does not see itself. By applying vision and drawing inferences from it, one can come to know the role eyes play in seeing, even though one never sees one's own eyes. Similarly, things in themselves and the transcendental self could be known if the proper methods were applied for uncovering the conditions that constitute experience, even though such conditions do not themselves appear in experience. Even here, where epistemological issues are at the forefront, it is actually ontological concerns, viz. the ontological status of self and objects, that is really at stake. Western philosophy rarely escapes that ontological tilt. Those who accepted that both the self and its objects were unknowable except through reason, and that such reason(s) was their cause and purpose for existing - thus epistemologically and ontologically grounding everything in the mind and its ideas - were labeled Absolute Idealists (e.g., Schelling, Hegel, Bradley), since only such ideas are absolute while all else is relative to them.
With the exception of some epistemological idealists, what unites all the positions enumerated above, including the materialists, is that these positions are ontological. They are concerned with the ontological status of the objects of sense and thought, as well as the ontological nature of the self who knows. Mainstream Western philosophy since Plato and Aristotle has treated ontology and metaphysics as the ultimate philosophic pursuit, with epistemology's role being little more than to provide access and justification for one's ontological pursuits and commitments. Since many of what are decried as philosophy's excesses - such as skepticism, solipsism, sophistry - could be and were accused of deriving from overactive epistemological questioning, epistemology has often been held suspect, and in some theological formulations, considered entirely dispensable in favor of faith. Ontology is primary, and epistemology is either secondary or expendable.