Without proper attention to words and to the art of grammar, someone trained primarily in informal arguments, puzzles, fallacies, logic games, or detecting biases will eventually discover that he does not know what was being said, how things were being defined, and even how precisely to articulate his own view or a response to the views of others. He knows only a few strategies for finding the truth, and he has sharpened his skills somewhat by looking at arguments and fallacies, but not on the real patterns of principles that guide all reasoning. It will be easy for him to confuse disagreement with contradiction and end up treating every pair of opposing views as if the two people had said opposite things about the same subject in the same respect. Worst of all, this approach to reasoning and rationality, because it relies on a collection of rules, tricks, and principles, risks leading the student to think that one can choose one’s principles and commitments as if from a menu. But even that particular view, that one can choose one’s principles, is a philosophical theory itself, for which one must have evidence and arguments, evidence and arguments that one evaluates in depth as to their meaning and validity, which can only be done in a consistent and coherent way by someone who knows the full art and science of logic.
To be clear, informal arguments always have implied theories and commitments in them already and it is one of the goals of logic to help ourselves discover how to make all such implied claims as evident as possible. Furthermore, a puzzle usually sets up the questions for us in advance and does not allow us to question them. Saying what a word means, determining whether a sentence is even a statement, and clarifying how “all” and “some” and “only” and “if” have been used: all of these questions have already been answered by the setup of the puzzle. But they are precisely what the art of reasoning should teach us to do. The same is true of many “fallacy” lists. We give a name to an error in reasoning, and the student learns to put the name on a paragraph. But knowing a fallacy, how to avoid it, and how to correct it when we find it involves knowing a great deal about how language works, how words get their meanings, and what sentences imply in their grammar. If we cannot say what the sentence was doing, the label of the fallacy is just a name for something that we may be right about but in fact it is something that we do not really understand.
Inference without the grammar of statements is an incomplete tool. This is why, even in modern logic courses, the grammar of a formal language is defined first, whether the language is being developed by logicians for rigorous thinking or as a programming language for precise instructions to computers.