Science is built up of facts, as a house is with stones; but a collection of facts is no more a science than a heap of stones is a house. Henri Poincaré reminded thinkers that observation alone cannot generate profound understanding without the guiding framework of a hypothesis. The investigator must venture to imagine an underlying order, testing that bold guess against rigorous experiment. A hypothesis is valuable not because it is guaranteed to be correct, but because it exposes itself to contradiction, prompting sharper questions. True knowledge advances when honest skepticism meets creative intuition.