Quine and Ullian, C5 and C6

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Chapter 5: Testimony

• Claim: there are two primary uses to language. Getting knowledge from others, and getting others to do what we want them to do.
• Testimony is like a microscope: it extends the range of observation sentences we can come to know. We learn from others what observation sentence they have confirmed by their own testimony.
• We begin with the assumption that testimony is true, and often reinterpret utterances to make them true. We conclude someone is lying only after that is the simplest interpretation of significant evidence to that effect.
• Testimony is more reliable when multiply confirmed -- but the sources of the testimony must be independent!
• Common "knowledge" is an unreliable source of testimony.
• Claim: we cannot believe a claim that we know is impossible.
• Claim: we cannot will to believe something and believe it on those grounds alone.
• We do believe things on faith, of course. For example, faith in claims we cannot ourselves confirm of scientists.

Chapter 6: Hypotheses

• Although some rationalists have believed we could establish all truths working from self-evident truths; and some empiricists believed we could establish all truths working from self-evident truths and basic given experiences; we know that only the most basic logic can be constructed from self-evident truths. Natural science thus requires something more: hypotheses.
• We need to identify the virtues of hypotheses (Note: Q & U's virtues of hypotheses roughly correspond to what we earlier called the criteria for evaluating and comparing theories.)
  1. Conservatism: coherence with prior beliefs.
  2. Modesty: the hypothesis entails less than the alternative hypotheses.
  3. Simplicity: simpler hypotheses are better.
  4. Generality: wider range of application is better.
  5. Refutability: this is falsifiability.
• A note about simplicity: Quine contends that simplicity is subjective. Many of us do not believe that. For example, a measure called Kolmogorov complexity is objective: it says that one string or equation or any other statement A is simpler than another B if the smallest computer program that can generate that string A is smaller than the smallest computer program that can generate B.