Putting the tools of linguistic analysis to work, Macdonald focuses her attention on the word 'theory'. What do philosophers mean when they talk about philosophical 'theories'? And is it the same thing that scientists mean when they use the word 'theory'? Macdonald's answer is a categorical 'No'.She claims that, when scientists put forward theories, they do so to explain empirical facts. Scientists put forward hypotheses (eg, 'Earth is round' or 'physical objects are governed by laws of gravity'), which can then be verified (or falsified) by experiments and observations, leaving behind only plausible theories, and eliminating those that are refuted by factual evidence. Thus, Macdonald writes: 'Confirmation and refutation by fact is an essential part of the meaning of "theory" in its empirical sense.'If 'confirmation and refutation by fact' based on experiments is essential to the way that the word 'theory' is used by scientists, that provides a basis on which to examine whether philosophers use the word 'theory' in that way. And this is where Macdonald thinks philosophical theories differ from what scientists mean by the term: 'They cannot be tested. Every philosophical theory of perception is compatible with all perceptual facts.'According to Macdonald, philosophical theories cannot be tested. Is that true? What might she mean by this? Once again, she uses the philosophy of perception as her example.Two opposing positions in the philosophy of perception are direct realism and indirect realism. Direct realism is the view that we directly perceive external objects in the world around us. When I look out of my window, I directly see a tree - and the nature of my perceptual experience informs me (directly) about the nature of the tree. Indirect realism, on the other hand, is the view that I only ever indirectly perceive objects like trees. What I directly perceive are mental representations - i.e., ideas of trees - that are produced in my mind when my sense organs (e.g., my eyes) are stimulated in the right way and send signals to my brain. I learn about the world around via these ideas (also known as 'sense data') in my mind. Direct realism might seem more common-sensical, but indirect realism might seem better equipped to deal with the existence of illusory or hallucinatory experiences, where I am seemingly not perceiving the world the way it really is. Given all this, isn't it true to say that direct realists and indirect realists disagree on the facts?In a sense, yes. But Macdonald's point is that there is no disagreement on the phenomenological facts: facts about what it is like to have a perceptual experience. Both the direct realist and the indirect realist agree that, when I look out my window, I see a tree. What they disagree on is what it means to say that 'I see a tree' - they disagree on the mechanics of what is going on, or how best to explain the fact that I see a tree. Most importantly, for Macdonald, there's no empirical test available to draw a line between the two theories. We can't run an experiment to test for the truth of either theory because, on the level of experience, both parties agree that it's true to say: 'I see a tree.'Thus, the first step in Macdonald's meta-philosophical argument is to show that philosophical theories are not 'theories' in a scientific sense since they lack the essential criterion of being confirmed or refuted by fact. For this reason, she argues, philosophical theories, unlike scientific theories, are not in the business of discovering new facts.Q 14.    What conclusion can be inferred from Macdonald's argument regarding the disagreement between direct realists and indirect realists?a)  Macdonald implies that the disagreement between direct realists and indirect realists stems from their differing interpretations of the mechanics of perception.b)  Macdonald argues that direct realists and indirect realists ultimately agree on the underlying facts of perception, despite their differing theories.c)  Macdonald suggests that the disagreement between direct realists and indirect realists cannot be resolved through empirical testing.d)  All of the Above