Psychology defined and unified

Neither defining terms, nor unity of knowledge have ever been strong points of psychological science. Many psychologists, faced with bringing order to psychology’s diversity, or even offering a definition of psychology, have excused themselves and gone for a lie down. So, my choice for the most inspirational study in the last three years is Gregg Henriques’ (2004) ‘Psychology Defined’, which spearheads a bold move to both unify and define the discipline.

Henriques (2004) argues that psychology’s epistemological fissures can be healed by accepting that psychology has two main subject matters: psychological formalism and human psychology. Psychological formalism is the science of mind and includes the cognitive, behavioural and neuro- sciences. Henriques thinks ‘mind’ can be conceptualized as the set of ‘mental behaviours’ in a manner that unites and bridges the schisms between the behavioural and cognitive sciences.

Human psychology is a sub-discipline of psychological formalism essentially dealing with how humans differ from other animals. To explain the separation, Henriques puts forward the ‘Justification Hypothesis’, which holds that humans are marked out from other animals by a capacity to justify their own behaviour.

The ‘Justification Hypothesis’ also forms an important part of Henriques’ attempt to place psychology in the broader context of scientific knowledge. The ‘Tree of Knowledge System’, developed earlier (Henriques, 2003), posits four fundamental dimensions of complexity: matter, life, mind and culture. These directly relate to four fundamental domains of science: physical, biological, psychological and social. The ‘Justification Hypothesis’, therefore, links mind ‘upwards’ to culture and the science of psychology to the social sciences. In the opposite direction, ‘Behavioural Investment Theory’, links mind ‘downwards’ to life and theoretically unifies the psychological and biological sciences.

What, then, is achieved by the Tree of Knowledge System and creating two broad, logically consistent fields of psychology? Henriques (2004) argues that ideas will no longer be defined against each other, as has become common practice in psychology. Moreover, unifying structures do not just provide aesthetic pleasure or relief from theoretical uncertainty, but a motor for the generation of effective practice in both lab and clinic.

These ideas inspired two special issues of the Journal of Clinical Psychology (1 & 2). Some of the articles replying and responding are reviewed and discussed on my blog in a series of posts starting here.

Further reading

Henriques, G. R. (2003). The tree of knowledge system and the theoretical unification of psychology. Review of General Psychology, 7, 150-182.

Henriques, G. R. (2004) Psychology Defined. Journal of Clinical Psychology, 60(12), 1207-1221.