Mechanist theories of explanation are taken to be tremendously fruitful in philosophy of science, and especially in philosophy of biology. Among the undeniable advantages of mechanist theories of explanation are: (a) they provide a prima facie adequate theory of explanation for the biological sciences, and possibly in other special sciences (because, e.g., no universal laws are presupposed, and the reference to part-whole relations in the explanatory practice of these disciplines is taken seriously), (b) they account for general as well as actual causal explanations, (c) they cope with several notorious counterexamples to many other theories of explanation (e.g., various scenarios of preemption, counting out irrelevant factors etc.). In this contribution, I would like to critically examine a specific account of mechanistic explanation, namely the account of Daniel Sirtes.