I think there is a causal link between nominalism/conceptualism epistemology and voluntarism. Nominalism/conceptualism consider ideas in our minds as the source of concepts rather then real essences in things in the world outside our minds, as moderate realism believes. Voluntarism is the philosophical doctrine that the will is a fundamental or dominant factor in the individual or the universe. I believe this doctrine came from a percieved reduction in the range of reason starting with nominalist and conceptualist epistemology. Moderate realism believes humans know universal essences from an immaterial power in the intellect in the soul. This is the first act of the mind, abstraction. This is followed by the 2nd and 3rd acts of the mind using these universal concepts in the acts of reason. Nominalism denies the existence of universal concepts by which we know real essences, rather nominalism believes these are just collections of things we assign names to. I think nominalism and conceptualism lead to the denial of realist metaphysics which is asserts that change is real in the world, that there are such things as potentiality and actuality of things. Actuality is the existence and act of the potentiality powers and nature of a thing. Metaphysical realities are transcendental qualities of a thing such as goodness, beauty, truth, the four cause of things (final,formal,efficient and effective causes) and other essential real concepts. Voluntarism rise when the role of the intellect in decisions is lowered. One of the most extreme examples of this is Nietzche’s will to power, which is an important principle of his approach to governing the world. In these days there is a humanism which has become a religion of humanity which demands a false moralism that believes that there is nothing higher than the human to search for in being human. This leaves the intellect as a less important power then the will in choices, in my opinion. Thus we are left with a voluntaristic approach to philosophy and a relativistic approach.