Since you refer to my book review in the Related Posts, I feel I am obligated to say Lord Kelvin and leave it to the readers to look at the review and see why I say that.
While you could argue that any of the men that Keithley honors is a genius, he bestows that honor on only one: James Clerk Maxwell. While we all know about his famous equations,
Dave van Ess of Cypress Semiconductor (http://www.cypress.com/?id=2201&month=3&year=2111 ) is fond of noting that the form of Maxwell's equations that we know and love (!!!!) was in fact developed from Maxwell's original formulae by Oliver Heaviside. Irrespective of who was responsible, if my career was to have been built on the understanding of any form of Maxwell's equations, I would have been selling shoes.
Who of the famous scientists, whether or not covered in Keithley's book, do you credit most for the job you have today?
In fact I credit some not so famous scientist and engineers- those many engineers who write app. notes especially the early Intel App Notes and the National Semiconductor Linear Application Notes.