What difference is there between sufficient reason and cause? We understand very well. Cause is never sufficient. One must say that the causality principle poses a necessary cause, but never a sufficient one. We must distinguish between necessary cause and sufficient reason. What distinguishes them evidently is that the cause of a thing is always something else. The cause of A is B, the cause of B is C, etc..... An indefinite series of causes. Sufficient reason is not at all something other than the thing.