Ockham's Razor is the principle that, when devising theories to explain stuff, theoretical entities should not be multiplied unnecessarily. It is used by some to justify atheism, and theism by others; but in fact it's useless. Consider how we would actually explain some observations: You see a cat walking behind a sofa, then just the sofa, and then a very similar cat emerges from behind the other side of the sofa. A natural way to proceed is to perceive one cat walking behind a sofa. You could imagine there were two cattish things in succession, but it's obviously more realistic to postulate the one cat.
......Was that an application of Ockham's Razor, or a trivial application of common sense? If it was Ockham's Razor, then why not postulate, instead of all such cats (and dogs and sofas and so forth) in the world, just the one demon, who has hypnotised us... oh yes, because that's obviously unrealistic! Similarly we could regard all the electrons and positrons in the world as a single electron going forwards and backwards in time, at least mathematically, but should we think of that as what actually happens, and believe in just the one electron? Ockham's Razor says we should (if it says anything); but what do you think?
......Where Ockham's Razor does seem clearly applicable (e.g. I don't explain the appearance of the cat from behind the sofa by postulating a cat and an invisible and intangible splodge of stuff quite unlike anything else) there's no need to apply anything other than a more general principle, such as that one's beliefs should be reasonable (a belief in such a splodge would clearly have no reason for being; it's only philosophers who would think of such a thing). So insofar as it's true it's unnecessary, and so it ought not (by it's own application) to be one of our principles.