Hi. I'm Dr. Anadale.
Let's take a quick look at the requirements of the five different types of justification of claims.
The first type of justification is justification by definition and I think this has two requirements
you should take note of.
First, it requires that you yourself know the definition of the term.
And second, it requires that your audience accept that definition and agree that it is legitimate.
I think it's the second requirement that undermines any attempt to try to justify belief in God
by appealing to the definition of God as the being that necessarily exists.
Any person who is skeptical about the existence of God is unlikely to accept such a definition,
and so it never really gets off the ground as a method of justification in that case.
The second type of justification is justification by perception. What does this require?
I think it requires first, that your sense organs be in proper working order, that you
don't have astigmatism or some other defect, that you be able to see without your glasses
if you were not wearing your glasses at the time you saw the accident, let's say.
It also requires an appropriate context for those sense organs to operate in.
So, if it was quite foggy on the night of the accident, when I thought I saw the red
car crash into the blue car, or if I was extremely far away from the accident, too far for me
to be able to see without my glasses, we might not trust my justification my perception in that case.
If the entire scene was lit up with red light, so my judgment of color was off because of
the distorting effect of the light--that's the context requirement that fails to be met
that would undermine my attempts to justify my belief that, let's say, I saw the red car
strike the blue car in the accident at the intersection.
That would undermine that attempt at justification by perception.
The third type of justification is justification by testimony, and I think this requires, first
and foremost, trust in the person giving the testimony.
You have to believe that they're telling you the truth, and then if they're testifying
about something that is in their own perceptual experience, then I have to meet, on their
behalf, both of the two requirements of justification by perception.
I have to believe that their eyes or ears were working properly and in the correct context;
there was no intervening circumstance that interfered with the operation of their sense
organs in this case.
The fourth type of justification is justification by authority, and like justification by testimony
it requires a kind of trust in the person giving the authoritative statement.
It also requires, though, that I satisfy myself that this person has relevant expertise.
And that actually opens up a whole new area for argument and dispute:
What kind of expertise is relevant?
What kind of credential do we need to find this person having?
We will see this maybe in the case of court cases where we have competing expert witnesses
put on the stand by the prosecution and the defense.
Who should we trust, as the jury, who should we trust about the proper interpretation of
the genetics evidence in this particular case? (for example)
So, evaluating credentials, then, turns out to be a whole area of further argumentation
when we're deciding who to trust, whose authority to trust when we have competing authorities,
where we have uncertainty authorities.
The fifth type of justification is justification by reasoning.
This is the one that we rely on very heavily in this philosophy class.
This has only two requirements.
First, that the premises we're appealing to be true and justified, or be reliable,
to use David Morrow's term.
And also that the premises, taken all together, support the conclusion that we are looking
at, that they have this logical relationship of entailing or making likely the conclusion
of the argument.
One of the key differences, I think, between this fifth type of justification and the first
four is, first, that it doesn't require an explicit trust in another individual, the
way justification by testimony and by authority seems to.
There's a sense in which, when I've worked through the logic of the argument and the
reliability of the premises for myself, I'm very much the owner of that conclusion.
There's a sense in which, even if I were Robinson Crusoe alone on a desert island for 15 years,
I could still use justification by reasoning without any other people to appeal to, provided
that my input premises were correct than my logical reasoning faculties were intact, I
would be able to do this all day long.
So there's a kind of autonomy I think to justification by reasoning that makes it attractive to philosophers.
And I think, unlike the first two types of justification, justification by reasoning
doesn't require as much contextual support.
It doesn't require that I verify that parts of my body are working correctly or that the
lighting etc. in some particular circumstance was correct, and it doesn't require that I
get the agreement of my audience for the definition that I'm using or that I'm appealing to.
All it requires is that I have a reliable set of starting points for my argument, that
the evidence is reliable, and that I can reason forward logically to the conclusion that that
evidence requires or points towards.
There's a sense, I think, in which, even if I were deprived of most all my senses and
were in a sensory deprivation tank, or paralyzed in bed with... unable to use my hearing or
my vision, I would still be able to reason through, to justify a claim by reasoning,
by logical reasoning.
So I think those are two important features that this kind of justification by reasoning
is so important in the study of philosophy.
How that comes... [laughter] So those are two important ways I think justification
by reasoning is different from the other four types of justification.
That's all for right now.
I hope you found this look at the requirements of the different kinds of justification helpful.
Thanks for watching today; goodbye.