In the late nineteenth century psychology initially adopted introspection, the systematic examination of one’s own conscious experience, as a primary method, most famously associated with Wilhelm Wundt, who established the first experimental psychology laboratory in Leipzig in 1879, and later with Edward Bradford Titchener, whose structuralist programme in the early 1900s attempted to catalogue the elements of consciousness through trained self-observation. However, critics argued that such reports were subjective, inconsistent, and difficult to verify experimentally, leading to increasing methodological dissatisfaction. The decisive institutional rejection came with John B. Watson, whose 1913 manifesto, “Psychology as the Behaviorist Views It,” launched behaviourism, declaring psychology an objective natural science concerned solely with observable behaviour and explicitly stating that introspection “forms no essential part of its methods.”

Behaviourists such as B. F. Skinner extended this approach during the 1930s–1950s, emphasising experimental control, prediction, and conditioning, which helped make psychology more experimentally rigorous but also effectively marginalised the study of subjective consciousness for several decades until the cognitive revolution of the 1950s–1960s reopened scientific discussion of internal mental processes. While this shift strengthened methodological objectivity and measurable experimentation, it also represented a loss: the early introspective tradition sought to understand the first-person structure of experience, something that purely behavioural data cannot fully capture, and modern psychology still relies on indirect forms of introspection such as self-report, interviews, and phenomenological description.

From a Christian perspective, the abandonment of introspection may also be viewed as a partial loss of attention to the inner life of the person, which Scripture treats as central to moral and spiritual knowledge: “Examine yourselves” (2 Corinthians 13:5), “Search me, O God, and know my heart” (Psalm 139:23–24), and “Keep your heart with all vigilance” (Proverbs 4:23), all implying a reflective awareness of the inner person before God. All streams of classical Christian theology, from Augustine of Hippo in Confessions to John Calvin in Institutes of the Christian Religion, similarly emphasised self-examination as a path to the knowledge of both self and God, suggesting that while the behaviourist rejection of introspection helped psychology gain scientific credibility, it may also have narrowed the discipline’s engagement with the deeper moral and spiritual dimensions of human consciousness that theology historically regarded as essential.