“I don’t think. I know.” We’ve all heard this, and most of us have probably uttered this phrase ourselves a time or two. But when you think about it (no pun intended), this phrase represents a misuse of language. It sets up a contrast between thinking and knowing, wherein “thinking” denotes uncertainty and “knowing” denotes certainty. While this may reflect a popular connotation of these words, denotatively speaking, neither has anything to do with certainty.
“Think” is a description of what the mind does. It describes the mind’s activity. Knowledge is “justified, true belief.” Certainty is not part of the definition, and thus certainty is not required for knowledge. To know something only requires that we have adequate justification.
If knowledge required certainty, then there is very little we could claim to know (the laws of logic, mathematics, and analytical truths such as “a bachelor is an unmarried male”). Most things we claim to know we cannot be certain of, and yet we are still justified in claiming to know them because we have good justification to believe they are true. For example, I know that my car is in my driveway right now even though I can’t see it. I can’t be certain of this since it’s always possible that someone stole it while I’m typing this, or that my wife drove to the store recently without my knowledge, but I am still justified in claiming to know my car is in the driveway.
Furthermore, it’s clear that “think” is not opposed to “knowledge” or “certainty” because we necessarily have thoughts about that which we know or are certain of. For example, I am certain that 2+2=4 and that bachelors are unmarried males. To have certain knowledge of these facts, I must also have the thought that “2+2=4” and the thought that “bachelors are unmarried males”. And if I have thoughts about them, then it is appropriate to say “I think 2+2=4” and “I think that bachelors are unmarried males.” One simply cannot know something without also thinking about it, and thinking it to be true.