Observability and Scientific Realism It is commonly thought that the
birth of modern natural science was made possible by an intellectual
shift from a mainly abstract and specuJative conception of the world to
a carefully elaborated image based on observations. There is some grain
of truth in this claim, but this grain depends very much on what one
takes observation to be. In the philosophy of science of our century,
observation has been practically equated with sense perception. This is
understandable if we think of the attitude of radical empiricism that
inspired Ernst Mach and the philosophers of the Vienna Circle, who
powerfully influenced our century's philosophy of science. However, this
was not the atti tude of the f ounders of modern science: Galileo, f or
example, expressed in a f amous passage of the Assayer the conviction
that perceptual features of the world are merely subjective, and are
produced in the 'anima!' by the motion and impacts of unobservable
particles that are endowed uniquely with mathematically expressible
properties, and which are therefore the real features of the world.
Moreover, on other occasions, when defending the Copernican theory, he
explicitly remarked that in admitting that the Sun is static and the
Earth turns on its own axis, 'reason must do violence to the sense', and
that it is thanks to this violence that one can know the tme
constitution of the universe.