By Gary Tedman
Philosophy, as it exists officially (academic and institutional), has a professional relationship to the sciences: it defends them, elucidates them, and provides a framework through which we can think them, especially in their combination. It tries to tell us what they mean, in human terms: how should we live our lives, according to science? You might say this is the function or purpose of philosophy today, it is its job.
Philosophy as we know it comes in two main strands, materialism and idealism.
Materialism is opposed to Idealism in the "theory of knowledge" - in the theory of how knowledge is derived. In the jargon, the "theory of knowledge" is called epistemology. For a Materialist, being (existence) comes before thought: you must be, first, in order to think. Idealists hold the contrary view: ideas come before existence. Note that we must not confuse the strict philosophical meaning of materialism with the casual sense of love of money and the things it can buy.
Marxism is essentially a materialist theory, but added to its theory of knowledge is always the dialectic, which furnishes the conception of development and change. This idea of development is known in philosophy as ontology, the theory of being or existence. So we have epistemology and ontology: materialism + dialectics, or dialectical materialism.
The dialectic was initially taken over by Marx from Hegel, the great idealist philosopher, but in a transformed way. To put it very schematically, Marx brought this process down to earth so that, afterwards, material (economic) factors determined social change in history, and not the human spirit or ideas. The resultant philosophy is materially "determinist," in that material factors cause events.
Determinism is the philosophical principle that material events that take place (in time) are caused by material events that happened previously, hence the simple idea of cause and effect in history. These causes can be worked out empirically, studied, tested, and in some cases reproduced, and so can also be predicted. This is a fundamental procedure of science (e.g. it leads to advances in technological products).