Of the two, whereby acts more like a relative pronoun; thereby, more like a demonstrative. whereby : by which (means), through which (means) thereby : by that (means), through that (means); because of that, for that reason, by doing that A revolution is an act of violence whereby (= by which) one class shatters the authority of another. -- James MacGregor Burns No one in this world has ever lost money by underestimating the intelligence of the great masses of the plain people.
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