Rationality is supposed to be integral to our humanity. Indeed, the “sapiens” in homo sapiens is from the new Latin sapere, meaning know, learn and know how. As a matter of fact, our subspecies is actually homo sapiens sapiens. Does this mean we have twice the intellectual capacity of our extinct ancestors from the Pleistocene? Judging from history, I’m not too sure. To make good decisions, we clearly need to understand fundamental concepts like rationality and reason.
Generally speaking, philosophers divide rationality into theoretical and practical rationality. Theoretical rationality is about creating right judgements, opinions and beliefs from prior experiences, beliefs and opinions. Practical rationality is about creating evaluations that motivate us towards right actions, i.e., wise decisions.
In order for beliefs or decisions to be rational, they must pass a two-part test. First, our belief or decision must result from good reasons and not be arbitrary. Second, our belief or decision must result from a process that is known to reliably create true beliefs and decisions that achieve specified goals.
Let’s take opinions and decisions regarding climate change. My acceptance of the fact that human activities are producing greenhouse gases, which are materially affecting our climate with enormous risk for the future of our species is an example of theoretical rationality. It passes the first test because my judgement is based on credible reasons like the existence of empirical research and scientific consensus. It passes the second test because relying on experts and common sense is a reliable way to create new true beliefs.
I am applying practical rationality when I make a pro-active decision to change my voting, travel, eating and other economic behaviors to help address climate change. This decision is based on credible reasons such as a justified acceptance of the facts of climate change and recognition of the feasible steps that I can take as a citizen and participant the global economy.
My decision passed the first test of rationality. But has it passed the second? Will my decision reliably achieve a goal of addressing climate change? According to Gernot Wagner in But Will the Planet Notice? How Smart Economics Can Save the World, maybe not so much. He argues that only broad changes in global macroeconomic policy can be effective. My actions as an individual are irrelevant. If I persist, then am I being not just irrational but also self-righteous and self-defeating? What do you think?
Our principles fix what our life stands for, our aims create the light our life is bathed in, and our rationality, both individual and coordinate, defines and symbolizes the distance we have come from mere animality. It is by these means that our lives come to more than what they instrumentally yield. And by meaning more, our lives yield more. Robert Nozick, The Nature of Rationality.
Nozick, the Nature of Rationality, via http://web.pacuit.org/classes/rationality/rat-lec1-handout.pdf
Angeles, Dictionary of Philosophy, Pp. 238-239