Here, philosophers diverge. Some say (following Hume's reasoning and his constant conjunction relation between events) that a necessary causal relation exists between events when one is the inevitable outcome (=follows) the other. Others propound a weaker version: the necessity of the effect is hypothetical or conditional, given the laws of nature. Put differently: to say that A necessitates (=causes) B is no more than to say that it is a result of the laws of nature that when A happens, so does B. Hempel generalized this approach. He said that a statement of a fact (whether a private or a general fact) is explained only if deduced from other statements, at least one of which is a statement of a general scientific law. This is the "Covering Law Model" and it implies a symmetry between explaining and predicting (at least where private facts are concerned). If an event can be explained, it could have been predicted and vice versa. Needless to say that Hempel's approach did not get us nearer to solving the problems of causal priority and of indeterministic causation. The Empiricists went a step further. They stipulated that the laws of nature are contingencies and not necessary truths. Other chains of events are possible where the laws of nature are different. This is the same tired regularity theory in a more exotic guise. They are all descendants of Hume's definition of causality: "An object followed by another and where all the objects that resemble the first are followed by objects that resemble the second." Nothing in the world is, therefore, a causal necessity, events are only constantly conjoined. Regularities in our experience condition us to form the idea of causal necessity and to deduce that causes must generate events. Kant called this latter deduction "A bastard of the imagination, impregnated by experience" with no legitimate application in the world. It also constituted a theological impediment. God is considered to be "Causa Sui", His own cause. But any application of a causal chain or force, already assumes the existence of a cause. This existence cannot, therefore, be the outcome of the use made of it. God had to be recast as the uncaused cause of the existence of all things contingent and His existence necessitated no cause because He, himself, is necessary. This is flimsy stuff and it gets even flimsier when the issue of causal deviance is debated.