To form a valid predicate or conclusion about a premise must it first be founded that its subject exist?

In other words in deductive formal logic is it invalid to form a conclusion about thing which premises are not true, or where the subject does not exist. 

Example: Jesus Christ is coming back. Is just one conclusion one can make, but first it must it BE that the subjects existence be proven or deductively valid? How can we validly conclude anything without first concluding the thing in mention

"exists".

Update:

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  • Anonymous
    1 month ago
    Favourite answer

    It might be easier to think in terms of mathematics. Do "imaginary numbers" exist? Only as abstract concepts, yet we use formal logic to deal with them, don't we? DON'T WE? Of course we do, or at least those of us who have taken basic algebra do. . 

  • John P
    Lv 7
    1 month ago

    I think you mean 'found', rather than 'founded'.

  • 1 month ago

    The logic is "the study of truths (true statements) based solely on the terms they contain:" (The Compton's Interactive Encyclopedia 1995)

    Search for 16:44 in the following video

    https://www.youtube.com/watch?v=CbP9jiWX08U

    Youtube thumbnail

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