The aim ... is to provide a clear and rigorous basis for determining when a causal ordering can be said to hold between two variables or groups of variables in a model . . . . The concepts refer to a model-a system of equations-and not to the 'real' world the model purports to describe.

The social sciences, I thought, needed the same kind of rigor and the same mathematical underpinnings that had made the 'hard' sciences so brilliantly successful.

Engineers are not the only professional designers. Everyone designs who devises courses of action aimed at changing existing situations into preferred ones. The intellectual activity that produces material artefacts is no different fundamentally from the one that prescribes remedies for a sick patient or the one that devises a new sales plan for a company or a social welfare policy for a state.

Engineering, medicine, business, architecture and painting are concerned not with the necessary but with the contingent - not with how things are but with how they might be - in short, with design.

Human beings know a lot of things, some of which are true, and apply them. When we like the results, we call it wisdom.

The situation has provided a cue; this cue has given the expert access to information stored in memory, and the information provides the answer. Intuition is nothing more and nothing less than recognition.

Most of us really aren't horribly unique. There are 6 billion of us. Put 'em all in one room and very few would stand out as individuals. So maybe we ought to think of worth in terms of our ability to get along as a part of nature, rather than being the lords over nature