I was recently working from a textbook, doing practice problems. Based on the text, an argument is considered valid "if there is no logically possible situation in which the premises are true and the conclusion is false," logically possible meaning a situation that entails no contradiction. I take this to mean that there is some imaginable situation, not necessarily an actual situation, just a coherent one, where the conclusion can be false at the same time all the premises are true. Using those definitions, why would the following argument be considered invalid? In what logically possible situation would the conclusion be false at the same time the premise is true?
Biden is heavier than Obama.
Fatima cannot lift Obama.
So there is no way she can lift Biden.