Science Series – Part 1: I Think Therefore I Am

This is Part 1 of a 5-part series that I am writing on science and PT practice.

A little background. I am a science geek, I have been since I was a kid, long before I became a physical therapist. I also love philosophy, discourse, and reason and devoted a large amount of my time to this as an undergrad. When I hear physical therapists discuss Evidence-Based Practice, I find that many can sound really scientific but often make mistakes in logic – mistakes that science inherently avoids. Much of this has to do with a lack of understanding of the history of the philosophy of knowledge and how science accounts for these known issues of knowledge. So if you are not familiar with René Descartes, David Hume, William of Ockham, or Karl Popper – you may be missing something…

Philosophers have sought to find absolute knowledge for centuries. Absolute knowledge is something that can be known with 100% certainty. This has always been difficult to define. Almost anything that could be claimed to be known would always result in some kind of challenge taking that certainty below 100%. One of the best examples of this is Meditations on First Philosophy published in 1641 by René Descartes.

Meditations was an attempt by Descartes to break down all knowledge to only those things that we can know with absolute certainty and then build from there. I’m not going to give you a play by play of the entire treatise, you can download the book for free onto any computer or e-reader (all classical texts are free now). I’ll just jump to the conclusion – the butler did it.

It is in Meditations that Descartes developed the “Evil Demon” argument. What he points out is that there could be an “Evil Demon” that cannot be known or perceived who alters all of our reality so that we cannot trust any of our senses. Of course this is an unreasonable belief, but how do we KNOW with 100% certainty that this is not the case? If you are uncomfortable with this antiquated concept, you may also imagine the more contemporary allegory known as the brain in a vat. You may be more familiar with this – The Matrix made a lot of money off of this concept.

So in Descartes’ world of the Evil Demon, we cannot know anything about our external world with absolute certainty. We cannot even be sure of the existence of the world itself including other people and their thoughts. So what are we left with?

Well, three things according to Descartes:

  • Mathematics
  • Logic (deduction)
  • Self existence

Mathematics and logic exist because they are abstract tools not based in any kind of reality (they can be used to process knowledge, but are not knowledge themselves). That leaves you with only one thing that is absolutely certain – You exist. Not me, not your co-workers, not that guy who was talking to a lamppost this morning. Just you, YOU exist. That is all that you know for certain.

Hence Descartes famous line, “I think therefore I am” (Cogito ergo sum for the Latin nerds out there).

This is the primary problem of seeking knowledge – perceptions can be deceived and are not to be trusted. In its infancy, science went through a lot of growing pains with many dead ends to get around this problem. It is learning about these failures that we develop an understanding of modern science.

Continue to the next post, Part 2: Continuity of Nature.