In this paper, I argue in favor of necessitarianism, the view that dispositions, when stimulated, necessitate their manifestations. After introducing and clarifying what necessitarianism does and does not amount to, I provide reasons to support the view that dispositions once stimulated necessitate their manifestations according to the stimulating conditions and the relevant properties at stake. In this framework, I will propose a principle of causal relevance and some conditions for the possibility of interference that allow us to avoid the use (...) of ceteris paribus clauses. I then defend necessitarianism from recent attacks raised by, among others, Mumford and Anjum, noting that the antecedent strengthening test is a test for causal relevance that raises no difficulties for necessitarianism. (shrink)