Inferences & Statements : We learned earlier that an inference is a statement that follows from one or more other statements.
A statement is a proposition.
Sentences and Propositions : for any sentence, the meaning of that sentence is some proposition.
For any word, that word has a meaning.
For instance, the meaning of the word ‘cat’ is something like 4 legged, mammal that meows.
Just as words have meanings, sentences have meanings .
The meaning of a sentence is a proposition.
The cat is on the mat example : the meaning of the sentence ‘ the cat is on the mat.’ is that the cat is on the mat.
Walking on the beach example: the meaning of the sentence ‘I walked on the beach today and my girlfriend walked with me’ is that I walked on the beach today and that my girlfriend walked on the beach with me .
The laws of logic: are rules for making a correct inference P given a certain set of propositions Q 1-n .
For example, we might believe both the proposition that Socrates is a man and the proposition that all men are mortal .
The laws of logic tell us that from these propositions we can infer the other proposition that Socrates is mortal .
Arguments: And when we have one proposition (such as that Socrates is mortal) inferred from one or more other propositions (such as that Socrates is a man & that all men are mortal) we have an argument.
An argument is any instance in which an asserted proposition is supported by one or more others.
We might also say that we have an argument when we have one asserted proposition supported by reasons for the truth of that proposition.
Issues: What is raised when a proposition is in doubt or in question.
Questions: we might go as far as to say that an issue just is a question.
Intelligent life: we might, for instance, consider the issue of whether there is intelligent life in the universe outside of Earth and we might take the position that yes there is such intelligent life in the universe.
Safety belt law : Or we might ask whether the safety belt law is just and we might take the position that it isn’t.
Mac vs. Pc: Or we might ask whether Macintosh computers are better than PCs and we might hold the position that Mac’s are better.
Arguments & Positions: so when we take a position on an issue and support it with reasons we have given an argument.
Intelligent life: we give an argument if we hold that there is intelligent life in the universe outside Earth and we support this position with the reason that, say, evolution plus the DRAKE equation show that there is such intelligent life.
Safety Belt law: Or we might claim that the safety belt law is unjust because of a person’s right to control what happens in and to her body.
Mac vs. Pc: Or we might claim that Mac’s are better than PC’s and give as a reason for our claim that Mac’s are much more user friendly than PC’s.