Justification via Other's Beliefs

We justify our beliefs using a combination of intuition, emotion, reasoning, sensory perception, and other means.

We may also justify our beliefs using other’s beliefs. For example, someone may believe that the sun’s light comes from nuclear reactions because their teacher believes it. Alternatively, one could listen to why their teacher believes the sun’s light comes from nuclear reactions, study the requisite math and physics, and judge for themself whether their teacher’s justification was valid.

In the first case, we are justifying our belief using another’s belief. In the second case we are adopting another’s justification for ourself without relying on their belief.

Frequently, we combine these approaches; for example, we may study enough nuclear physics to feel comfortable accepting our teacher’s opinion. In this case, we are justifying our belief partially on our own knowledge and reasoning, and partly on our teacher’s belief.

When we justify our beliefs using other’s beliefs, we open ourselves up to two problems:

  1. The other person is deceiving us.
  2. The other person is mistaken.

Given these problems, when is it appropriate to justify our beliefs using other’s beliefs?

Many beliefs can only be justified via other’s beliefs. Beliefs that prophets have had religious revelations fall into this category. For example, a prophet says that God wants you to stop going on expensive vacations and to donate to the poor. You can only justify your belief in the prophet by believing what the prophet says; you must believe that they are not deceiving you and they are not mistaken. Beliefs about historical events can only be justified via other’s beliefs because we are not present to see the event ourself. For example, your Uncle tells you that your great great grandfather had Parkinson’s disease; nobody else in the family knows about this and there are no records, and you must make a difficult personal medical decision using this knowledge. Your belief that you have a family history of Parkinson’s is based on your Uncle’s belief.

When considering such beliefs, we must build a supporting case for our own belief. We must consider the other person’s motives, how many other people also belief the same thing (for example, our belief in the Holocaust is based on the witness of many people).

Other beliefs may be justified by other means, but only at great difficulty. For example, the experimental evidence for our theory of nuclear reactions in the sun would be difficult for me to reproduce.

Typically we rely on other’s beliefs when we do not have the time, interest, or ability to understand their justification ourself.

If we take the time to understand the other person’s justification we may avoid the first problem. But we can not completely avoid the second problem, because we may be mistaken ourself.