The question as to whether scientific theories can be shown to be true or false is a complex one. The answer depends on one's interpretation of the meaning of theory. To what does it refer? Is its role to reveal the nature of reality, or is it merely a human construct? In which case what do we mean by truth? Is it an accurate description of reality, or does it simply refer to a successful theory that produces accurate predictions? Duhem attacks this problem from a very strict non-metaphysical standpoint. As a result he shows that we can know nothing about material reality, and indeed very little about the validity of our own theories. In the end it appears that the theoretical framework within which scientists work is more a matter of convention than anything else.
In order to determine whether the claim that scientific theory cannot be proven true or otherwise we must first understand what Duhem means by scientific theory.
He introduces two possibilities as to the nature of a physical (which we can equate to 'scientific') theory. The first being that it is an explanation of the reality lying behind a group of experimental laws (those that are empirically determined). The second is that a physical theory is simply an abstract system to classify and summarize a group of laws.
Taking the first possibility (a belief still held by many today): this seeks to look beneath the sensible appearances and find the reality beneath, which is causing the sensations we experience. However, this presents us with a problem. We only have access to perceptions so how can we hope to find a physical theory that provides a certain explanation of the reality causing these sensations? A theory can only suggest a reality that would produce all those...