One of Whewell's great influences was Joseph Butler. Whewell's admiration of Butler was not uncritical, however. In the following selection, Whewell indicates what he sees as the major flaw in Butler's approach, in a way that sheds further light on issues like moral progress and discovery.
I have already observed that while, among the defenders of Independent Morality, Clarke, in stating his moral opinions, entangled himself by adopting the terms of the prevalent metaphysical system, Butler too often perplexed his readers by trying to avoid all systematic metaphysics. But this mode of treating the subject does not answer the needs of those who pursue it as a speculative study. For short technical expressions, when they are familiar to us, enable us to avoid much labour of the intellect which we must otherwise incur; and to fix our attention at once upon the critical part of each proposition and argument. If there shall be found to be introduced afterwards a technical classification of the faculties and operations of the human mind, which shall be consistent with the truths asserted by Butler, the business of understanding his arguments will be much simplified. We may conceive that, in his enquiries, he was doing that which, in fact, discoverers always have to do. They search at the same time for true propositions and for precise definitions. Each of these elements depends upon the other; they are found at the same time, and approximated to by the same degrees. MEn go on towards moral as they go on towards physical truth. The proposition that the planets are directed bya central force, became more and more certain as the conception of a central force became more and more clear. We have already compared Cudworth to Kepler, who was confident there was such a force, yet most vague and loose in his description of it: perhaps not even Butler can be compared with Newton, who laid down the law of this force with complete evidence, and traced it to its remotest effects. He rather resembles Borelli or Wren or Huyghens, who referred this force to its true center, and saw with entire conviction the certainty of its operation, but wavered from one form of expression to another in their description of its nature; and though they asserted its existence, did not lay down its law in words, nor draw out a system of its consequences.