Dmitry Chernikov’s Blog

In the first philosophy book I ever read, Philosophy for Dummies by Thomas Morris (which is a brilliant introduction to numerous philosophical ideas), Morris articulates the “principle of belief conservation.” First he argues that some of our beliefs are rational, or else the term “rational belief” would have neither referent nor meaning. The usefulness of this term comes from being able to separate rational beliefs from ir- or non-rational ones. Common sense supports the view that our belief acquisition faculties are at least sometimes reliable.

Here’s the principle. For any proposition, P: If

1. Taking a certain cognitive stance toward P (for example, believing it, rejecting it, or withholding judgment) would require rejecting or doubting a vast number of your current beliefs.
2. You have no independent positive reason to reject or doubt all those other beliefs, and
3. You have no compelling reason to take up that cognitive stance towards P,

then it is more rational for you not to take that cognitive stance toward P.

“Your current beliefs,” Morris goes on, “are like a raft or boat on which you are floating, sailing across the seas of life. You need to make repairs and additions during your voyage. But it can never be rational to destroy the boat totally while out on an open sea, hoping somehow to be able to rebuild it from scratch, or else to swim without it.” (72ff)

The principle passes its own test and is elevated into a basic belief.

I think this opinion is similar to what Victor Reppert has proposed, namely that one should keep believing what one already believes, unless one encounters a good reason to believe otherwise.