The infinitely small neither have nor can have theory; it is a dangerous instrument in the hands of beginners [...] anticipating, for my part, the judgement of posterity, I would dare predict that this method will be accused one day, and rightly, of having retarded the progress of the mathematical sciences.
The poetic beauty of Davy's mind never seems to have left him. To that circumstance I would ascribe the distinguishing feature in his character, and in his discoveries,—a vivid imagination sketching out new tracts in regions unexplored, for the judgement to select those leading to the recesses of abstract truth.
Of Humphry Davy
George Boole took up Leibniz's idea, and wrote a book he called The Laws of Thought. The laws he formulated are now called Boolean algebra... Boole seems to have had a grandiose vision about the applicability of his algebraic methods to practical problems—his book makes it clear that he hoped these laws would be used to settle practical questions. William Stanley Jevons heard of Boole's work, and undertook to build a machine to make calculations in Boolean algebra. He successfully designed and built... the Logical Piano... the first machine to do mechanical inference.