Sometimes it is not easy to determine what constitutes the principal content of a given philosophical system. And by no means is it always possible to base oneself on the opinion of the very thinker in question. Thus, for example, there is Marx's valid comment, "What Spinoza believed to be the cornerstone of his system, and what actually constitutes that cornerstone, are two different things entirely." It is not always easy to find the "key" to the content of a system (...) in its history either, for the perception of ideas and the attitude to them bear the imprint of the given era and, as time passes, much changes in the way in which these ideas are understood. (shrink)