The Immaterial Self

Foster's The Immaterial Self presents a rigorous philosophical defense of substance dualism, arguing that human persons possess immaterial minds or souls distinct from their physical bodies. Writing against the prevailing materialism of late twentieth-century philosophy of mind, Foster develops a systematic case for why conscious experience cannot be adequately explained by purely physical processes, and why personal identity requires an immaterial substrate.

The work proceeds through careful analysis of the phenomenology of consciousness and the logic of personal identity. Foster contends that the qualitative nature of conscious states—their subjective, first-person character—resists reduction to physical descriptions. He examines various materialist attempts to explain consciousness, including functionalism and identity theory, arguing that each fails to capture the essential features of mental life. His critique extends to property dualism, which he finds unstable and ultimately collapsing into either materialism or substance dualism.

Central to Foster's argument is his treatment of personal identity through time. He maintains that neither physical continuity nor psychological continuity theories can adequately account for the persistence of persons. Instead, he argues that personal identity requires a simple, indivisible substance—an immaterial self—that underlies and unifies conscious experience across time. This substance is not merely a collection of mental properties but a fundamental entity in which these properties inhere.

While Foster does not explicitly develop a theistic argument, his defense of immaterial souls has clear implications for debates about God's existence. By establishing the coherence and necessity of non-physical substances, he provides philosophical space for divine existence and action. His arguments counter the naturalistic assumption that reality consists solely of physical entities governed by natural laws. The work thus contributes to natural theology by undermining physicalist premises that often support atheistic conclusions.

Foster engages primarily with contemporary analytic philosophers, particularly those defending materialist theories of mind. His method combines phenomenological analysis with rigorous logical argumentation, drawing on both empirical considerations about consciousness and a priori reasoning about the nature of substances and properties. The work represents a significant challenge to the materialist consensus in philosophy of mind, offering sophisticated arguments that continue to influence discussions about consciousness, personal identity, and the fundamental nature of human beings.