  Knowledge internalism and externalism have been less extensively discussed in recent literature than justification internalism and externalism. These two opposing theses focus on justified belief rather than knowledge, though there are close parallels. Consider again the Canada geese example, and suppose that the testimony you receive from another person produces in you the justified belief that there are geese in the park. We may also suppose that this justified belief falls short of knowledge. We can say that a justifier for this belief is the testimony one has received from the other person. Here a justifier is an analog of what was termed above a knowledge basis and, as in the latter case, we will allow that justifiers can be other beliefs, or experiences, or facts about the production of the belief. Philosophers take different stances on what legitimate justifiers may be, so that it is difficult to come up with an account of justifiers that is neutral between competing theories of epistemic justification. It will not do to say that everything relevant to a person's justified belief at some time counts as a justifier for that belief. For that would count possession of the concepts that are necessary for one to understand a belief that p as among the justifiers for that belief, and clearly that would be a mistake. Instead, we can say this: The justifiers for a given justified belief are those items that make up or constitute the person's justification for that belief at that time. They are those items, whether experiences, states of affairs, or other beliefs, on which the person's current justification is based. (the term ‘justifier’ comes from Alston 1989, 189).