Idealism serves as a general umbrella term for a variety of traditions of thought which find expression as early as the pre-Socratic philosophers, continuing through tenets of Medieval Scholastics to pre-Cartesian thinkers and Descartes himself. Berkeley, on of the three great British empiricists, is most often credited with formulating the basic tenet of idealism, i.e. 'esse est percipi/to be is to be peceived'. After idealism flourished and was unified, however, as a coherent and influential line thought in the early-mid 19th-century in Germany, the basic philosophical doctrine had been made explicit: reality is somehow mind-dependent or mind-correlative, in that the physical objects of the world can not be separated from mind-cognizing activity. A simplified and somewhat critical view of this basic tenet holds that mind constructs reality. But idealism in general simply holds the irrefutable position that no external reality or physical universe nor its litany of objects may be regarded without recourse to the cognizing activity of the mind. If an object is perceived, modeled, discussed or theorized, it is necessarily in relation to the thoughts of the mind. The critical (and often misconceived) disctinction in the characterization of idealism may be stated: there may be thought-independend objects 'out there', but this cannot be determined or verified (remaining hypothetical) as any object engaged with in the universe is so through being thought about. For explanatory purposes, objects cannot be referred to without reference to minds.

Though this primordial idealist tenet is difficult to refute, it remains so only as a very basic parameter. And after Kant's Transcendental idealism/Critical Realism, idealism has offered differening positions with respect to just what the functioning of the mind entails then for reality. Absolute Idealism asserts that 'the mind' is behind nature or outside of finite minds; Cosmic Idealism identifies mind more with nature as a pervasive, abiding force or impulse; Social Idealism identifies the mind with the sui generis collection of all individual minds; and Personal Idealism tends towards an distributed collection of individual minds. Such positions vary greatly in their metaphysical corrollaries, yet all hold a basic antagonism to a 'common sense' or 'naive realism' which maintains that external objects exist exactly as we know them. For the various idealists such an operating assumption begs the question: how can we be sure of such a one-to-one correspondence relationship?

Such a critical exploration of the relationship between mind and reality was exhaustively addressed by Kant who concluded that 'things-in-themselves' or the contents of an indepenent reality may exist (and commonsensically they do) yet we cannot have direct knowledge of them as what is perceived and thought about is always mediated by the innate conceptual wiring of the mind. Basically, we only perceive reality in so far as our minds are structured to perceive reality. Such a settlement creates an unsatisfying vicious circle, as well as leaves an ambiguity with respect to the real, or things-in-themselves: if such elemental building blocks of reality are not directly cognizable, how are they to be related to the rest of our mind's activities, especially since an apparent insuperable divide had been established between Being - the real and our engagement with it - and mind.

Variations to the proposed solutions to such a dilemma continue to flourish in new guises, though undoubtedly the most systematic and ambitious schemes are represented by Fichte, Schelling and Hegel of the German Absolute Idealism of the 19th-century. Building upon Fichte's transformation of Kantianism, Hegel's philosophy of "the rational is the real and the real is the rational" synthesized the antithesis of mind and reality in one encompassing process of the unfolding of infinite spirit/Geist. In this temporal process the finite, or individuated mind and things-in-themselves, and the infinite merge in a sui generis movement.

For archaeology, the influence of idealism is present but less apparent due to the historical fortunes of idealism as a unified metaphysics. After the transformation of idealism by Kierkegaard, Marx, Engels and others in the mid-19th-century, shifting focus more towards individual autonomy and material dialectics, idealism retained a predominance in British philosophy until the end of the century, but never re-gained a popular and widespread adherence. Rather, the movement to materialism and positivism excluded all but a few isolated departments or philosophers - such as Royce, Bradley and Bosanquet - espousing the importance of mind-mediation. Nevertheless, idealism later became an undercurrent of thought in the reaction against phenomenalist and materialist-driven philosophy - a philosophy which had self-consciously moulded itself as simply a 'hand-maiden' to science. With a revival of metaphysics (not at all prevalent even still in Anglo-american philosophy departments,) in Continental Philosophy and as 'grounded' with Phenomenology, idealist precepts may be detected in the rise of social constructivism, in the critical, 'negative dialectics' (though spun from 'Left Hegelianism') of the Frankfurt School and its brand of Marxism, in material culture studies of objectification, and even in post-Kuhnian Philosophy of Science. Such schools of thought, rather than idealism per se, may be detected in later British archaeology reacting against positivist doctrines of the discipline.