However, from the human point of view action is the ultimate thing. We merely establish the fact that he chooses and acts and that we are at a loss to use the methods of the natural sciences for answering the question why he acts this way and not otherwise. Natural science does not render the future predictable. It makes it possible to foretell the results to be obtained by definite actions. Our ignorance with regard to these two spheres taints all human actions with uncertainty.
Apodictic certainty is only within the orbit of the deductive system of aprioristic theory.
The most that can be attained with regard to reality is probability. This problem is without practical importance for praxeological considerations. At any rate, the theorems of physics and chemistry have such a high degree of probability that we are entitled to call them certain for all practical purposes. We can practically forecast the working of a machine constructed according to the rules of scientific technology. But the construction of a machine is only a part in a broader program that aims at supplying the consumers with the machine's products.