Tron is a high tier, well known discord debater. He has a server dedicated of teaching newbies on debating
Here's an example of it:
Formal Logic
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In short terms, formal logic deals with the deductive validity of relationships and inference steps/argumentations. This is evaluated using mathematical symbols and syllogisms. Deductive logic is the systematic evaluation of arguments for internal cogency, with the internal cogency being dealt with here being logical validity. A logical validity is formed when a premise AND conclusion is true, which would form a deductively valid argumentation. When this is established, it is logically impossible for the premise to be true and the conclusion to be false.
Speaking of which, when the premise is true and the conclusion is entailed to be false, this would form a deductively invalid argumentation. In this case, your conclusion doesn't guarantee any logical truth/truth values even if granted for the premise. Let's go ahead and look at some examples of this.
A
(1) Either Bob is at school or he is at BestBuy
(2) Bob is not at school
(3) Bob is at BestBuy
Looking at this inference step, we can see that this is clearly a deductively valid argumentation. A1 and A2 both entail a logical truth logically following to the conclusion, which also guarantees a logical truth. Therefore, there's no possible reason for A3 to be false.
But what about one that IS NOT deductively valid? Let's take a look.
B
(1) All Republican voters support capital punishment.
(2) Jo supports capital punishment.
So (3) Jo is a Republican voter.
This is clearly logically invalid. Even if B1 and B2 are true, B3 doesn't logically follow from all Republican voters supporting capital punishment. This conclusion doesn't guarantee a truth value and hence this inference step is deductively invalid.