Belief is mentioned later in the article, clarifying the meaning. But be assured: knowledge is only ever a form of belief. The laws of physics could change tomorrow (this is not precluded by any provable rule of existence). Really everything we know, we know inductively. (Mathematical knowledge is excluded from this obviously because of its weird, tautological nature--but within math, the discovery of non-Euclidean geometry is a good example of things that were thought to be necessarily true turning out to be merely axiomatic)

Another example of "knowledge" being used in the sense meant by the article is this:

"It ain't what you don't know that gets you into trouble. It's what you know for sure that just ain't so." --Mark Twain