Practical Reasons

Consider two very different questions:

(1) Does God exist?
(2) Should one believe that God exists?

Even if the answer to (1) is negative or inconclusive, the answer to (2) might very well be affirmative. For even if there are no intellectual or evidential reasons for affirming (1), there might be reasons for affirming (2); and if there are any reasons for affirming (2), it follows that there are practical or prudential reasons for affirming (1).

One practical argument ties theism to happiness in the hereafter:  <Pascal's Wager> (an article I did for the Internet Encyclopedia of Philosophy).

Another practical argument ties theism to happiness in the here-and-now:  William James's Will to Believe.

Yet another practical argument ties theism to one's sense of self:   the Argument from Identity.