René Descartes’ Dualism, articulated in Meditations on First Philosophy (1641), proposes that the human being is composed of two fundamentally distinct substances: res cogitans (the thinking, non-extended mind) and res extensa (the extended, material body). This was a bold claim grounded in his method of radical doubt and crystallised in the insight cogito, ergo sum, which affirms the certainty of conscious selfhood even while the physical world is questioned. By separating mental substance from bodily mechanism, Descartes inaugurated the modern mind–brain problem and opened space for scientific investigation of the body without denying the irreducibility of subjective experience. From a Christian perspective, Descartes’ view resonates with Biblical affirmations of the soul’s reality and value, such as Jesus’ distinction between body and soul in Matthew 10:28 and Paul’s tripartite language of spirit, soul, and body in 1 Thessalonians 5:23, while also echoing the imago Dei doctrine (Genesis 1:27), which grounds human dignity in a God-given rational and spiritual nature. Yet Christian critique notes that Descartes’ sharp substance dualism risks overstating separation where Scripture emphasises holistic unity (Psalm 139:13–16; 1 Corinthians 6:19–20), potentially encouraging a neglect of embodied life and communal responsibility. Even so, the enduring value of Cartesian Dualism lies in its insistence that persons are more than biological machines. For personal wellbeing, it legitimises inner life, conscience, prayer, and reflective self-care as real and causally significant. For societal health, it undergirds human rights, moral accountability, and compassionate ethics by affirming that each individual possesses an inviolable inner worth not reducible to material utility, thereby continuing to inspire dialogue between science, philosophy, theology, and humane social practice.