When does one act based on the predominance of probability, and when does one not, and what is its governing principle?

The one afflicted with obsessive doubts should turn away from them and ignore them. If such doubts occur during prayer, he should build upon the greater number. The principle is to act based on certainty, and if certainty is unattainable, then strong presumption takes its place. Indeed, strong presumption has been treated as equivalent to certainty in many rulings due to the impossibility or difficulty of attaining certainty. Jurists differ in the applications of this principle.