deductive
In deductive reasoning, you start from a given set of rules and conditions to determine what must be true.
For example: A mammal breathes oxygen and gives birth to live young. A whale breathes oxygen and gives birth to live young. Using deductive reasoning, a whale must be a mammal.
Another example: Class starts at 8:00am and I must be there by 8:00am to be on time. It is 8:05am and I am not in class. Using deductive reasoning, I am not on time for class.