“Leibniz wanted to combine physics, mathematics, logic, and philosophy, and he would no doubt have loved this joke: An engineer, a mathematician, a logician, and a philosopher were traveling through Scotland when they saw a black sheep through the window of the train. "Aha", says the engineer, "I see that Scottish sheep are black." "Hmm", says the mathematician, "You mean that some Scottish sheep are black." "No", says the logician, "All we know is that there is at least one black sheep in Scotland." "And even", the philosopher continued, "The only thing we can be really sure of is that the side facing us is black.”
Book:Homo Informatix