Ockham's maxim is spelled: Entia non sunt multiplicanda praeter necessitatem. The meaning of which being that it is bad scientific method to introduce, at once, independent hypotheses to explain the same facts of observation. In this regard, I did respond to Noel Carroll's question about parsimony (Ockham's razor) in calling forth Ricoeur's point that the facts that psychoanalysis seeks to explain are different from those that cognitive science or neuroscience seek to explain. They are simply not the same facts. According to principle of parsimony, as Peirce reminds us: "Before you try a complicated hypothesis, you should make sure that no simplification of it will explain the facts equally well."
Brief Reply to Burnett on Ockham
Now here's something for Colin to chew on regarding Occamism (from Peirce's "A Neglected Argument for the Reality of God"):
"Modern science has been builded after the model of Galileo, who founded it, on il lume naturale. That truly inspired prophet had said that, of two hypotheses, the simpler is to be preferred; but I was formerly one of those who, in our dull self-conceit fancying ourselves more sly than he, twisted the maxim to mean the logically simpler, the one that adds the least to what has been observed, in spite of three obvious objections: first, that so there was no support for any hypothesis; secondly, that by the same token we ought to content ourselves with simply formulating the special observations actually made; and thirdly, that every advance of science that further opens the truth to our view discloses a world of unexpected complications. It was not until long experience forced me to realize that subsequent discoveries were every time showing I had been wrong, while those who understood the maxim as Galileo had done, early unlocked the secret, that the scales fell from my eyes and my mind awoke to the broad and flaming daylight that it is the simpler Hypothesis in the sense of the more facile and natural, the one that instinct suggests, that must be preferred; for the reason that, unless man have a natural bent in accordance with nature's, he has no chance of understanding nature at all. Many tests of this principal and positive fact, relating as well to my own studies as to the researches of others, have confirmed me in this opinion; and when I shall come to set them forth in a book, their array will convince everybody. Oh, no! I am forgetting that armour, impenetrable by accurate thought, in which the rank and file of minds are clad! They may, for example, get the notion that my proposition involves a denial of the rigidity of the laws of association: it would be quite on a par with much that is current. I do not mean that logical simplicity is a consideration of no value at all, but only that its value is badly secondary to that of simplicity in the other sense.
If, however, the maxim is correct in Galileo's sense, whence it follows that man has, in some degree, a divinatory power, primary or derived, like that of a wasp or a bird, then instances swarm to show that a certain altogether peculiar confidence in a hypothesis, not to be confounded with rash cocksureness, has a very appreciable value as a sign of the truth of the hypothesis."