Probabilistic reasoning is the opposite of black and white thinking.
When you reason in black and white you ask questions like: Is this true? Is this the right thing to do? Am I sick?
When you reason probabilistically you ask questions like: How likely is this? What's the expected value of this action? What evidence have I seen that I am sick, and what evidence that I'm not? How likely is it that I'm sick without taking any evidence into account?...