According to Naive Realism, things are in reality as the senses depict them. Human sense organs determine the truth or falsity of objects and conclusions. Only that which is subject to first-hand observation is verifiable. The expression, “I'm from Missouri, I have to be shown,” exemplifies this criterion, the idea being, “Unless I see it, I will not believe it.”

William S. Sahakian, Ph.D.
Ideas of the Great Philosophers

There is only the reality of direct perception, supplemented by the reality that is directly and “naturally” inferable (common-sensical) on the basis of such perception:

John Dewey

In this brief reference to facts that are perfectly familiar, I have tried to suggest three points of crucial importance for a naive realism: first, that inferential or evidential knowledge (that involving logical relation) is in the field as an obvious and undisputed case of knowledge; second, that this function, although embodying the logical relation, is itself a natural and specifically detectable process among natural things — it is not a non-natural or epistemological relation; third, that the use, practical and scientific, of perceptual events in the evidential or inferential function is such as to make them become objects of inquiry and limits of knowledge, and to such a degree that this acquired characteristic quite overshadows, in many cases, their primary nature.

from Chapter 9: "Naive Realism versus Presentative Realism"
John Dewey, Essays in Experimental Logic

Thus, when the doorbell rings, it is “natural” or a matter of “common sense” to infer that, above and beyond the mere sensory impression of the sound itself, (a) that sound I hear is, in fact, the doorbell ringing; and even (b) there is a person (or someone or something) on the other side of the door. And thus, naive realism includes the “someone” or “something” inferred to be on the other side of the door in reality.

Simple materialism frequently pits itself against exoteric religion, declaring that, because they can’t be perceived with the senses, there is no God or greater Spiritual Reality. Because there is no Greater Reality (and an associated imperative to right living and a higher moral order), a common conclusion is to live on the basis of “Eat, drink, and be merry, for tomorrow we shall die.”

If materialism were simply a helpful viewpoint for explaining a portion of reality that would be one thing. But materialism in practice also presumes itself to be a complete philosophy capable of accounting for everything; thus, it functions as a reductionistic methodology for understanding reality, presuming that whatever is currently inexplicable in material terms will someday be completely understood in and “reduced” to material terms. Just as there is no God, there is no thing that is “inherently unknowable”, only that which is currently (and temporarily) unknown. (We examine this reductionistic methodology in greater detail a little later.)

As a formally organized Western philosophy, materialism can be traced back at least as far as the philosopher, Thales of Miletus (c. 580 BC). Aristotle wrote that Thales was the first to suggest a single material substratum for the entire universe (water). But Thales’ philosophical significance lies not in his choice of water as the essential substance, but rather in his attempt to reductionistically explain all of reality in terms of water (a visible material), rather than in terms of the caprices of (anthropomorphic and invisible) gods.

While the East traditionally has been non-materialistic in its outlook, one Indian school — the Carvaka school of Materialists — did flourish from around the 6th century BC until medieval times.