In non-specialist contexts, to ask for the cause of some particular happening is to ask what made it happen, or brought it about. To give a causal explanation is to answer such questions, usually by specifying some prior event, condition, or state of affairs without which the problematic event would not have occurred. In more specialist, scientific or philosophical contexts, the concepts of cause and causal explanation have been the focus of sustained attempts to achieve analytical rigour. Medieval European thought on this topic was dominated by Aristotle's doctrine of the ‘four causes’. These were efficient cause (roughly corresponding to the commonsense view just outlined); material cause (the nature or composition of a being); formal cause (its form or structure); and, fourthly, final cause (its goal or purpose).
Advocates of the scientific revolution which took place in the 16th and 17th centuries were prone to anti-Aristotelian polemics. In the increasingly successful mechanical view of nature there was no place for explanations in terms of goals or purposes, except in the domain of human intentional activity. Indeed, some radical advocates of mechanical explanation (for example Thomas Hobbes) extended its scope even to this latter domain. Empiricists, in particular, were hostile to all attempts at explanation in terms of supposed entities or properties not accessible to observational or experimental determination. The search for not only final but also material and formal cause, as these were commonly understood, should be abandoned in favour of a programme of explanation in terms of efficient causality.
Empiricism became the dominant philosophical representation of scientific method, and it has been particularly influential in shaping popular views of the nature of science. The 18th-century philosopher David Hume is generally credited with the empiricist view of efficient causality as a regular association, or ‘constant conjunction’ of phenomena in our experience. If events of one type (B) are regularly preceded by events of another type (A), then we may identify A as the cause of B. But this drastic narrowing-down of causal explanation to what could be established by the evidence of the senses only served to underline the gap between scientific claims and their basis in evidence. Hume famously posed the intractable problem of induction; namely, how do we know that regularities in our experience so far will be continued into the future? Or, more generally, how can we make justifiable inferences from our finite evidence to the universal claims embodied in causal laws? Hume appeared content to acknowledge that no such rational justification could be found, but empiricist philosophy since Hume has been littered with failed attempts to solve this problem. It should be noted that, in the absence of a solution to the problem of induction, empiricist philosophy can give no rational justification for counterfactuals, scientific prediction, or for the application of scientific knowledge in new technologies.
But there are other difficulties faced by the empiricist view of causality, now commonly referred to as the ‘covering law’ account (that is, the event to be explained is shown to be ‘covered’ by a law linking events of that type with events of some other type). The most obvious of these is that events may be regularly associated with one another without one being the cause of the other (in the sense of bringing it about, or making it happen). The association may be coincidental; or, more likely, there may be some more complicated causal connection between them (such as that both are effects of some so-far undetected common cause). A related problem is that even where the evidence suggests a direct causal relation between two phenomena, it may not be possible to establish which is the cause, and which is the effect.