Critiques of introspection have played a pivotal role in shaping the evolution of psychology from a speculative philosophy into a rigorous science. In the late 19th and early 20th centuries, introspection, the method of examining one's own conscious thoughts, faced intense scrutiny. Foremost among its critics was John B. Watson, who in 1913 famously rejected introspection in his "Psychology as the Behaviorist Views It," arguing that subjective reports were unreliable and unverifiable. This bold stance catalysed the rise of behaviourism, shifting the field toward observable, measurable behaviour. Later, B.F. Skinner further entrenched this view in the 1930s and 1940s, emphasizing empirical methods and dismissing mental states as scientifically irrelevant. Even Karl Popper, the philosopher of science, criticised Freudian introspective methods in the 1950s, labelling them unfalsifiable and thus unscientific. These critiques collectively ushered in a new era for psychology, one grounded in experimentation and objectivity, paving the way for cognitive science and neuroscience to emerge with more sophisticated tools to explore the mind. Many today would argue that an effective psychology relies on a range of different research methods to advance its understanding. Quantitative and qualitative studies can both increase our knowledge, and the capacity to reflect on our own thinking certainly plays a key part in this. Healthy introspection is encouraged in the Bible, particularly in relation to faith. For example, Saint Paul writes, “Examine yourselves as to whether you are in the faith” (2 Corinthians 13:5).