What then is an empiricist? In this text, we will use the following definition of empiricism:
Empiricism … is the epistemology that asserts that the evidence of sense constitutes the primary data of all knowledge; that knowl- edge cannot exist unless this evidence has first been gathered; and that all subsequent intel- lectual processes must use this evidence and only this evidence in framing valid propositions about the real world.
It is important to highlight a number of terms in Robinson’s definition. First, this definition asserts that sensory experience constitutes the primary data of all knowledge; it does not say that such experi- ence alone constitutes knowledge. Second, it asserts that knowledge cannot exist until sensory evidence has first been gathered; so for the empiricist, attain- ing knowledge begins with sensory experience. Third, all subsequent intellectual processes must focus on sensory experience in formulating propositions about the world. Thus, it is not the recognition of mental processes that distinguishes the empiricist from the rationalist; rather, it is what those thought processes are focused on. Again, most epistemolog- ical approaches use sensory experience as part of consisted only of matter and motion and that both could be understood in terms of mechanistic prin- ciples. Why, asked Hobbes, could not humans too be viewed as machines consisting of nothing but matter and motion? Galileo was able to explain the motion of physical objects in terms of the external forces acting on them—that is, without appealing to inner states or essences. Are not humans part of nature, wondered Hobbes, and if so, cannot their behavior also be explained likewise?