Men are not the only beings that operate in groups, but the human species embarked upon a unique line of development because man had the capacity to make and use tools. The very act of making tools was a stimulus to increasing rationality rather than the consequence of a fully matured intellect. In historical terms, man the worker was every bit as important as man the thinker, because the work with tools liberated men from sheer physical necessity, so that he could impose himself upon other more powerful species and upon nature itself. The tools with which men work and the manner in which they organize their labor are both important indices of social development.