[PL 211] Absence of evidence & evidence of absence

The fallacy known as appeal to ignorance has two forms:

• The fact that p is not known to be false is taken as a reason to believe that p is true.

 For example:

1. We don't know that it is not the case that Pegasus exists.
2. Therefore, Pegasus exists.

More schematically:

1. We don't know that not-p.
2. Therefore, p.

• The fact that p is not known to be true is taken as a reason to believe that p is false.

For example:

1. We don't know that it is the case that Pegasus exists.
2. Therefore, Pegasus does not exist.

More schematically:

1. We don't know that p.
2. Therefore, not-p.

Now, suppose that one argues as follows:

1. We don't know that it is the case that Pegasus exists.
2. Therefore, to all intents and purposes, Pegasus does not exist.

Similarly:

1. We don't know that it is not the case that Pegasus exists. 
2. Therefore, to all intents and purposes, Pegasus exists.

Which of these, if any, seems like a legitimate inference to make?