Because, for, since, as, inasmuch as are the chief causal conjunctions in English.
Because assigns a cause or reason immediately and explicitly; as, I hid myself, because [=for the express reason that, or as caused to do so by the fact that] I was afraid; he must have passed this way, because [=owing to the specific fact that] there is no other road or because [=as is directly proved by the fact that] his footprints are here.
For is a particle of less immediate reference than because; it regards the statement to which it is subjoined as relatively independent and proceeds to adduce for it some ground, reason, evidence, proof, explanation, or justification; as, I hid myself, for [=as I may add by way of explanation] I was afraid; he must have passed this way, for [=as you may readily see] here are his footprints; I like him, for [=I ask, in justification of the fact] who can help it?
Since is less formal and more incidental than because; as assigns a reason even more casually than since; each of them frequently begins its sentence; as, Since (or As) I was afraid, I hid myself .
Inasmuch as assigns a reason in a somewhat concessive or qualified fashion; as, Inasmuch as [=in view of, or considering, the fact that] I was afraid, I hid myself; I am ready to accept your proposal, inasmuch as [=seeing that] I believe it is the best you can offer.