To take one example: Aristotle laid down the foundation of what became modern science. Modern science became modern science as we think of it by rebelling against Aristotle's a priori assumptions; without Aristotle, what science we have today would be very different, indeed.

I don't think you can so easily dismiss Plato, Aristotle, Descartes, et al: without them we we wouldn't be where we are today.

This is part of the problem I often detected at OB and see again here at LW: people with little respect for intellectual history.