The word “rationality” carries a lot of historical baggage and cultural misconceptions, enough so that I have considered not using it at all. Yet a substantial portion of my social circle has decided to adopt this label (spoiler alert!), and for better or worse, it is the label that I use in my own mind. First I am going to address what rationality is not, before talking about this definition of rationality and why we should care about it.

Cartesian Rationality and Axiomatic Systems

The first widespread use of rationalism was a philosophy espoused by Descartes back in the 17th century. In this sense, the opposite of rationalism was empiricism. Rationalism as a philosophy in its extremest form holds that the only source of knowledge or justification is through our own reason. Descartes himself tried to derive all of the “eternal truths” of mathematics, epistemology, and metaphysics through the single starting assumption of cogito ergo sum – I think, therefore I am.

While not every thinker believes that reason is the only source of knowledge, it does have the connotations of conscious deliberation being the primary source of knowledge, or morality, or action. Even a rudimentary reading of cognitive science clearly shows that our brain is a massively-paralleled and mostly unconscious processing machine, with a very small deliberation module attached on top (and particularly connected with verbal processing). Anyone hoping to utilize their reasoning needs to understand where it comes from and what purpose it serves, to avoid deluding themselves and going horribly wrong. [Read more…]