The dominant theory of thinking is the dual system theory as elegantly described by David Hardman in his book Judgment and Decision Making. Psychological Perspectives. This theory recognises two categories of thinking:
- The intuitive or the subconscious
- The analytical, reflective, or Bayesian.

In his book Thinking, Fast and Slow, Daniel Kahneman refers to intuitive thinking as System 1 thinking. This is the fast cognitive mechanism which ‘operates automatically and cannot be turned off at will’, but is however prone to error because it ignores uncertainty and doubt. Kahneman also refers to analytical thinking as System 2 thinking; this is the slow and deliberate process that takes into consideration uncertainty and doubt. Hardman posits that most people rely on the intuitive process because of the ease with which it generates opinions and decisions.

Whilst these two thinking processes appear to be separate, Hardman stressed that there is a ‘continuum between the intuitive and reflective‘ mechanisms. In this regard, the cognitive continuum theory has been proposed to take into account the observation that the two forms of thinking lie on a spectrum. According to Sue and colleagues writing on clinical decision making in the book A Foundation for Neontal Care: a Multi-disiplinary Guide, the cognitive continuum theory plays down the divide between the two thinking processes because ‘reasoning is neither purely intuitive nor purely analytical but is rather a continuum between the two poles, with judgements located at points somewhere in between’.

In essence therefore, the two theories are sides of the same coin. In the following blog posts, we will tackle the intuitive or unconscious thinking process, before proceeding to explore the analytical.