In this paper I briefly compare some of the divergent reasons given by Leibniz and Hume for their common criticism against the idea of liberty of indifference. For Leibniz, the harmonic connection among concrete individual substances is expressed exclusively by means of relations that are intrinsic to their complete concepts, so that indifference can only exist within the sphere of incomplete notions or concepts of reason, the only one where it is possible to isolate a few terms and relations from all the infinite others that compose the complete substances. In Hume, there is a de facto impossibility of stepping out of the regularity of the extrinsic causal relations, which, by means of the application of general rules, ends up encompassing the whole of experience, albeit without any rational guarantee. In consequence, he confines indifference to a quasi ficticious native state of the mind, which precedes experience, or else to the limited sphere of a few situations that make this native state reappear within experience itself.