the parts are false, and can be invalid even if some parts are true. But a valid form with true premises will always have a true conclusion. For example, consider the form of the following symbological track: All meat comes from animals. All beef is meat. Therefore, all beef comes from animals. If the premises are true, then the conclusion is necessarily true, too. Now we turn to an invalid form. All A are B. All C are B. Therefore, all C are A. To show that this form is invalid, we demonstrate how it can lead from true premises to a false conclusion. All apples are fruit. (True) All bananas are fruit. (True) Therefore, all bananas are apples. (False) A valid argument with a false premise may lead to a false conclusion, (this and the following examples do not follow the Greek syllogism): All tall people are French. (False) John Lennon was tall. (True) Therefore, John Lennon was French. (False) When a valid argument is used to derive a false conclusion from a false premise, the inference is valid because it follows the form of a correct inference. A valid argument can also be used to derive a true conclusion from a false premise: All tall people are musicians. (Valid, False) John Lennon was tall. (Valid, True) Therefore, John Lennon was a musician. (Valid, True) In this case we have one false premise and one true premise where a true conclusion has been inferred. Example for definition #2 Evidence: It is the early 1950s and you are an American stationed in the Soviet Union. You read in the Moscow newspaper that a soccer team from a small city in Siberia starts winning game after game. The team even defeats the Moscow team. Inference: The small city in Siberia is not a small city anymore. The Soviets are working on their own nuclear or high-value secret weapons program. Knowns: The Soviet Union is a command economy: people and material are told where to go and what to do. The small city was remote and historically had never distinguished itself; its soccer season was typically short because of the weather. Explanation: In a command economy, people and material are moved where they are needed. Large cities might field good teams due to the greater availability of high quality players; and teams that can practice longer (weather, facilities) can reasonably be expected