 Sometimes, Boyle remarks, our ignorance of things has to do simply with our lack of knowledge of the inner or hidden workings of a thing. He offers his, and indeed the century’s, standard example of clocks which may have various internal mechanisms to produce the same outer effects. Thus he remarks that “we know in general, that digestion is made by some Menstruum or subtile substance in the Stomach; thô we know not the particular nature of that substance, (as whether it be Acid, Urinous, &amp;c.)”. Sometimes, though, our ignorance is of a deeper, richer variety: