Is it permissible to act upon the dominant assumption in all matters, such as prayer and ablution, or not?

If a person is afflicted with obsessive doubts (waswas), they must disregard these doubts. However, if they are not afflicted with obsessive doubts, the default principle is to act upon certainty and build upon the minimum, unless that becomes impossible, in which case they should act upon the prevailing assumption (ghalabat al-dhann). In the scenarios mentioned, if the person is not afflicted with obsessive doubts, they should act upon certainty, such as not reciting (if unsure whether they did), praying three rak'ats instead of four (if unsure about the number), and not washing their hands from impurity (if uncertain about its presence). Some scholars permit acting upon the prevailing assumption in certain matters.