連結動詞は何ですか？

Before moving on to the main discussion of Moore's Proof, it is worth summarizing the sceptical argument, rooted in the thought of Descartes. Many philosophers have asked the question of whether we can have knowledge of the existence of external world, but the sceptical argument has not conceded that such knowledge is possible. Descartes, in First Meditation, suggests that, "As if I did not recall having been deceived before by just such thoughts in sleep! When I think more carefully about this, I see so plainly that sleep and waking can never be distinguished by any certain signs, that I am bewildered; and this itself confirms the idea of my being asleep." (Descartes, 1641). We cannot even know that we are either dreaming or awake, and our perception gives us no conclusive or certain knowledge about the external world. So our perceptual justification for our beliefs about the world outside our mind is not defensible. This negative philosophical conclusion became the basis of philosophical scepticism.

緯度の線に別の名前は何ですか？

P1. Here is one hand
P2. Here is another
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C1. Therefore, two hands exist
C2. Therefore, two external objects exist

中世のフレッチャーは何ですか？

Moore shows what he considers to be "a perfectly rigorous proof" of the existence of things outside of us, and it is "probably impossible to give a better or more rigorous proof of anything." (PEW) For him, the best way of proving the existence of something is to simply find it right before our eyes; he provides another example with the case of misprints on a page. The best way to prove whether the misprints exist is that we look and find that here is one misprint, and here is another, and here is another. Therefore we prove that there are three misprints on the page. That, Moore thinks, thoroughly proven. (Because this way of proof is in some favour at the middle of 20th century, the proof is assimilated and reconfigured by the ordinary language philosophers, such as Norman Malcolm and Alice Ambrose. But their interpretations were vigorously repudiated by Moore.)

In addition, the proof surely satisfies, according to Moore, three logical conditionals: (1) the premise is distinct from the conclusion; (2) the person knows the premises to be true; and (3) the conclusion follows from the premises. It seems right that the proof meets the (1) and (3) conditionals because the premises of his proof above (here is a hand and here is another) are clearly distinct from the conclusion, and the conclusion follows the premises. Nevertheless, the most problematic point of his proof is on the (2) conditional, "the person knows the premise to be true," which means the percipient knows he/she has two hands. Indeed the sceptic's criticism focuses on this suggestion, but also this is the most significant point for understanding Moore's intentions.

We shall now look more carefully into this matter, because it is obvious that the premises lead to the first conclusion (C1) but it is not obvious that the first conclusion entails the second conclusion (C2). Landesman (1999) explains this logical gap between two conclusions. In brief, external objects, such as one's own hand, a tree, and so on, are physical things that are perceivable and that exist independently of being perceived in contrast to such private objects as visual afterimages. Moore's hands are paradigm cases of external physical objects. This means that from the fact that, for example, hands exist, it follows that there exist objects that are perceivable and independent and that count as external objects. If someone thought he saw a hand, but it turned out that what he saw did not exist independently of the perception of it, then it would follow that he did not actually see a hand but was undergoing a hallucination of the hand.