the concept of a counterfactual theory of causation revolves around the belief that a singular event of series of events leads into another event in a logical course of order and action . In other words ,the “first event ‘ is the root cause of the “second event . So , it would be logical to assume that if the first event did not exist , then neither would have the second event as it was reliant upon the happening of the first event in order to exist . There have been a number of counterfactual theories of causation , but the most famous of these theories was the one defined by David Lewis .Like most contemporary counterfactual theories , Lewis ‘s theory employs a possible world semantics for counterfactuals . Such a semantics states truth conditions for counterfactuals in terms of relations among possible worlds . Lewis famously espouses a realism about possible worlds , according to which non-actual possible worlds are real concrete entities on a par with the actual world (Menzies )In a way , Lewis is stating that “semantics ‘ may refer to perceived realities as opposed to actual realities . In other words , an interpetation of an experience as opposed to the actual experience from a physical concrete standard . Lewis ‘ theory was never accepted as an ironclad truth and faced a bit of criticism and , later , self revision .However , most contemporary philosophers would seek to deploy the explanatorily fruitful possible worlds framework while distancing themselves from full-blown realism about possible worlds themselves . For example , many would propose to understand possible worlds as maximally consistent sets of propositions or even to treat them instrumentally as useful theoretical entities having no independent reality (Menzies ) In a way , it would be safe to assume that no events exist independent of external stimuli . That is , the concept the “cause and effect ‘theory of relationships between various events is a logical concept and Lewis ‘ work has a certain validity since it is based in a simliar logic .