They treat the institutions and assumptions by which they live as absolute, self-evident, and given.

From Plough, Sword and Book by Ernest Gellner. Page 11.

Men and societies frequently treat the institutions and assumptions by which they live as absolute, self-evident, and given. They may treat them as such without question, or they may endeavour to fortify them by some kind of proof.

In fact, human ideas and social forms are neither static nor given. In our age, this has become very obvious to most of us; and it has been obvious for quite some time. But any attempt at understanding of our collective or individual predicaments must needs be spelt out against the backcloth of a vision of human history. If our choices are neither self-evident nor for keeps, we need to know the range of alternatives from which they are drawn, the choices that others have made or which were imposed on them. We need to know the principles or factors which generate that range of options. The identification of those principles or factors is not beyond our capacities, even if specific prediction continues to elude us.

We inevitably assume a pattern of human history. There is simply no choice concerning whether we use such a pattern. We are, all of us, philosophical historians malgre nous, whether we wish it or not. The only choice we do have is whether we make our vision as explicit, coherent and compatible with available facts as we can, or whether we employ it more or less unconsciously and incoherently. If we do the latter, we risk using ideas without examination and criticism, passed off tacitly as some kind of "common sense".