When someone asks us whether a belief is justified, we often find ourselves wanting to answer both ‘‘Yes’’ and ‘‘No,’’ even when all other facts are settled. This ambivalence is a signal that we need to distinguish different ways in which a belief may be said to be justified. These distinctions are often overlooked, but the failure to draw them creates countless confusions in moral epistemology and in everyday life. Let’s try to do better.
His distinctions are a series of dichotomies. I'm not sure this is the best way to divide up types of justification, but it's certainly better than using an ambiguous term when more precision would be helpful.
Instrumentally vs. Epistemically Justified
In philosophy lingo, "instrumental" has to do with whatever it takes to get something done, often to the exclusion of other concerns. Think about how tools or instruments help get things done, without regard for whether it's something that should be done from a broader perspective.
Suppose an Atheist is married to a Theist and this is a source of conflict and unhappiness. The Atheist wishes she could manage to believe in God because her family life would be much improved. One day, an oddly credible stranger offers her a pill which will chemically alter the way she thinks so that she will believe God exists. She takes the pill, which works as advertised. Her new belief would be instrumentally justified because it's held for a reason that's good for the instrumental goal of having a happier family life.
The problem with instrumentally good reasons is that they are totally independent of truth. Sinnott-Armstrong's own example was a drug to make a person believe there are aardvarks on Mars for the goal of winning ten million dollars. Most people use "justified" to mean good reasons that have something to do with improving a belief's chance to be true; they intend epistemic justification. Epistemology is the philosophical study of knowledge, which requires beliefs to be true...not just useful.
Permissively vs. Positively Justified
I'm reluctant to call permissive justification a form of justification at all. A permissively justified belief is one that is not held for a bad reason, but not necessarily for any good reason either. If I have no reason to believe an external world exists outside my mind and no reason to believe the opposite, I would be permissively justified in believing either side. Why not just say it's permissible — but not justified — to believe something so long as it's not believed for a bad reason?
Positively justified beliefs are those I indicated in the first sentence of this post: beliefs held for a good reason (for some reason and not a bad reason).
Slightly vs. Adequately Justified
A belief is slightly justified when there is some good reason in favor of it being true, but not enough — given the context — to nullify good reasons in favor of something else being true instead.
Suppose a fingerprint is found at a crime scene. If it's matched to a man who isn't likely to have ever been to the scene otherwise, the fingerprint is a good reason to think he is the perpetrator. However, it might not be a good enough reason if there's also reason to think the perpetrator is very smart and the print was on something which could have been brought in to throw off the police. For a very serious crime like murder, the print may not adequately justify the belief the print-owner committed the crime compared to the belief he is being framed.
Slight and adequate justification could probably be split up into several finer-grained distinctions.
Personally vs. Impersonally Justified ...and Wholly Justified
The basic idea here is that a person can be personally justified if she does all the things we can reasonably expect a person to do in order to have good reasons for her beliefs. Unfortunately and despite our best efforts, we are always somewhat vulnerable to false or limited information.
Suppose a practical joker went around to every clock and electronic device in the house and set them all one hour early, hoping to get a laugh when you leave for work early. You might be personally justified in believing it's time to go to work, but not impersonally justified. The third-person narrative of the facts shows a problem with your belief.
Sinnott-Armstrong gets into Gettier problems, which complicate matters. For this post I'll just say beliefs are wholly justified when they're both personally and impersonally justified.
1. Oxford University Press, 2006. Pg. 63.