Knowledge, Faith, and Belief

Words have meaning, and if we are going to communicate with each other we need to make sure to use words as carefully as we can.  Otherwise, misunderstandings abound.  It seems very common that a word like “faith” is used by different people for different ends, and the definition shifts even within an argument.  Take for example, this video:

Here there is a distinction drawn between “faith” and “belief”, using an analogy of a roller-coaster – belief in the ride being safe vs trusting it being safe enough to ride on.  As with many things, I find it far more useful to describe terms in probabilistic vocabulary.  Let’s start with belief.

We say we believe a proposition A when P(A)>0.5.  We say we believe strongly in a proposition A when P(A)>0.95 or some other, somewhat arbitrary, high number.  The strength of a belief is a scale.

What is knowledge?  I’ve heard philosophers give the following definition of knowledge:

Knowledge is justified true belief. [note: bad definition, IMO]

I am not satisfied with this definition because, it seems to me that, in order to justifiably label anything as knowledge with this definition we’d need to be able to independently determine that the proposition is true.  This  presupposes that there is some “outside” knowledge, which I feel comes too close to assuming a religious justification.  I do believe that there is probably a truth to be known, but that we can never truly know what it is for certain – but this is not a problem.  It is a red herring to bring up 100% certainty for knowledge, because it is never achievable, and isn’t what we practically call knowledge.  I prefer a definition inspired by Stephen J Gould:

In science, ‘fact’ can only mean ‘confirmed to such a degree that it would be perverse to withhold provisional assent.’ I suppose that apples might start to rise tomorrow, but the possibility does not merit equal time in physics classrooms.

Where it says “fact”, read “knowledge”.  Where it says “science” read “life”.  We label things as knowledge in our lives when they are “confirmed to such a degree that it would be perverse to withhold provisional assent.”  Thus, P(A)>0.9999 ~ 1.  Notice that we don’t need 100% certainty to claim knowledge, and that it is possible for the “knowledge” to be wrong.

What about faith?  Is faith “belief without evidence”, as atheists like to suggest?  Is it “trust”, as in the video above?  We could start with the Biblical reference,

Hebrews 11:1, “Now faith is confidence in what we hope for and assurance about what we do not see.” [NIV]

which I read as a synonym for “wishful thinking”.  Others may read it as “trust”.  Still others as “belief without evidence”, and perhaps there are more.  The problem here is that it doesn’t have a clear definition, so it fails in its usefulness.  What are people really claiming here?

Let’s go back to the roller-coaster example.  I would submit that, in this case, strong belief must be a prerequisite to “faith” in the sense he’s using it.  If you don’t believe the roller-coaster is safe, or you don’t believe the roller-coaster exists, then you cannot have trust it in.  Once you believe it is safe, do you trust it to ride?  This brings in decision theory, where we mix probabilities with utility measures.  You could believe it to be safe at the P(safe)=0.9 level, but still not trust it “with your life” because of the cost associated with being wrong.  So trust requires  both belief and a sufficiently positive net utility.  Placed in these terms it is much more clear how the argument is set up.

  • when the religious say that “faith” is like “trust”, they are already approaching the problem with strong belief, and are assessing utility – and they rightly claim that belief is not enough.
  • when the atheists say that “faith” is “belief without evidence”, they are addressing the strength of the evidence to obtain strong belief – and saying that it is not sufficient.
  • when the religious say that “faith is rational” they are either talking about utility, not belief, or they are claiming that the evidence is in fact good enough for strong belief, and then consequently high utility.

In all cases, it seems as if for the religious, utility and belief are muddled when using the word “faith”.  For the atheist, “faith” is always about belief.  Perhaps if we ditch the term “faith” altogether and focus on what we’re actually claiming it would make communication a lot easier!


About brianblais

I am a professor of Science and Technology at Bryant University in Smithfield, RI, and a research professor in the Institute for Brain and Neural Systems, Brown University. My research is in computational neuroscience and statistics. I teach physics, meteorology, astonomy, theoretical neuroscience, systems dynamics, artificial intelligence and robotics. My book, "Theory of Cortical Plasticity" (World Scientific, 2004), details a theory of learning and memory in the cortex, and presents the consequences and predictions of the theory. I am an avid python enthusiast, and a Bayesian (a la E. T. Jaynes), and love music.
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5 Responses to Knowledge, Faith, and Belief

  1. Tim says:

    When people use the terms “know” and “believe”, we cannot really know what they’re saying until we understand what those words constitute, for them.

    Suppose I’m standing in front of a rickety-looking bridge with a friend. I’m afraid to cross, so I look to my friend for advice. Now, consider the following two responses he might give:

    – “I believe this bridge is safe.”
    – “I know this bridge is safe.”

    Most people, I think, will immediately feel that the former response leaves them a little more wary than the latter. “I know” implies a higher level of certainty than “I believe”.

    We might get a clue as to why this is, if we think about the two follow-up questions I’m sure to ask:

    – If he said “believe”, I’d ask “WHY do you believe that?”
    – If he said “know” I’d as “HOW to you know that?”

    A response to the question “why do you believe X?” can take many forms, all of which can be valid reasons for X, but many of which might not be applicable to me, or anyone else, for that matter. “Because Susie told me so.”, “Because the moon is full tonight.”, “Because I’ve taken careful measurements and performed numerous tests.” All of these might be valid reasons “why” a person believes something.

    But the question “how do you know X?” is different, because “how” questions are different than “why” questions. If I ask you “How did you build that table?” you’d have to give me some very specific information, and I would expect to be able to reproduce it (assuming I have the skills), but if I ask “Why did you build that table?” the answer could be anything, and it might not have any bearing on my own interests or abilities.

    Suppose I venture across the bridge and it crumbles underneath me and I fall to my death. If my family were to sue, I think it might make a big difference whether my (former) friend said “believe” or “know”. If he said “believe”, my family’s lawyer might demand: “tell the jury WHY you believed that!” to which my friend might respond “because I had a fortune cookie the day before that told me to be more trusting”, and that would be the end of that. But if the word used was “know”, the lawyer has something to sink his teeth into. Not just any answer will do for “how did you know?”

    So anyway, before we can judge what to do when a person says “I know” or “I believe”, we have to know what his standards are.

  2. brianblais says:

    I don’t see any difference between “why do you believe X” and “how do you know X” other than the fact that knowledge entails a much higher probability, thus the sorts of evidence will be qualitatively different than merely establishing P(X) >0.5. Although the parallel construction “why did you *DO* X” (e.g. why did you build that table) looks similar, it is asking a very different question than the “why do you believe X”. Not all “why” questions are the same.

  3. Cait says:

    I really like this post, though realistically, I think we will (unfortunately) never be able to completely ax the term “faith.” I agree that it would be a much better world if people held the same definitions of abstract ideas.

    I like the Wikipedia page on “Faith and Rationality”, which is much like your definition of faith. It states, “Rationality is based on reason or evidence. Faith is belief in inspiration, revelation, or authority. The word faith generally refers to a belief that is held with lack of, in spite of or against reason or evidence”
    ( I think if people used the same terminology, and thus recognized that when they use the seemingly magical, attractive word “faith”, that they’re actually saying that they are holding onto a belief without or against evidence.

    Although not quite the same, this idea reminds me of the word “theory.” In layman’s terms, theory means personal belief or opinion. However, in science, it means almost the compete opposite. A scientific theory is as close as we have to “fact” (this term used loosely, because we can never know if something is entirely true) based on many different independent evidences, repeatable experiments, peer-review, observation and experiment, and coincidence with other existing “facts”. This is a term I wish we could ax this term, too, or at least get everyone on board with the same definition.

  4. Cait says:

    Woops… not “coincidence”…. I meant coincides.

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