Lack of a fundamental set of assumptions in physics encourages or often compels physicists to conceive different sets of assumptions (often unrelated) for different phenomena. When taken together, they often contradict each other. Because of numerous contemporary assumptions, physics is no longer an exact science. This affair can be remedied only by sorting out the existing assumptions and tabulating one basic (set of) fundamental assumption(s) on which the explanations for every physical phenomenon should depend. If any assumption in physics is ripe for re-thinking, I will suggest ‘actions at a distance through empty space’ as the first candidate.In our material world, all real entities are made of matter. The existence of matter is a solitary phenomenon without a prior cause. Therefore, the original assumption should be only with respect to the existence of matter. Further development of physics in all spheres should be based on this original assumption. To add to or modify original assumptions whenever certain phenomena are not readily explainable is an incorrect practice. The multitude of assumptions currently used in physics may be substituted by a single and basic assumption: ‘Substance is fundamental, and matter alone provides substance to all physical entities’. Although conclusions may diverge from current beliefs, reasoning based on this single fundamental assumption can logically explain all physical phenomena in nature.