Justification by..

Question

Give an example of each:

a belief that can be justified by definition,

belief that can be justified by perception,

belief that can be justified by testimony,

belief that can be justified by authority,

belief that can be justified by reasoning

Answer 1

Sorry, I accidentally put the answer in the comment. Here it is:

1. All dogs are mammals. This is part of what it means for something to be a dog. It is part of the definition of 'dog', and so the justification comes just by learning what 'dog' means. Something like "1+1=2" is also true by definition (meaning).

2. I exist. That is a belief that is justified simply from the fact that I perceive anything at all (a la Descartes). Others are "I have two hands." This is an example from GE Moore (called a 'Moorean fact').

3. Justin is having another baby. That is a belief that can be justified by Justin testifying that this is the case. This can run together with the next one a little bit. Another example is "The suspect shot the victim," which might be a belief a juror forms on the basis of eye witness testimony (and not really authority per se).

4. The US fought against Japan in WWII. This belief is based on the authority of history texts. Any historical belief would do. Similarly, scientific claims that are complex are like this. Even "water is h20" might work because, really we probably couldn't explain this well--we trust the chemists.

5. Today is Tuesday. I only believe this because I believe that yesterday was Wednesday (I had a particular appointment yesterday), and Tuesday always follows Wednesday. I reason from some claims to another belief about what day it is. Maybe a better example is a probabilistic claim like "The MLB will not hold a season in 2020." I might reason from the intractability of the arguments between the players and the league that it is highly likely that no season will commence. Thus, the belief is based on reasoning from other beliefs.