We have seen that the first step in argument is the interpretation of the proposition in order to resolve it into its essential parts; and we have seen that a first step in any such interpretation must be the definition of terms. Many fallacies are due to inadequate definition of terms, for the most dangerous source of verbal confusion and consequent dispute is our failure to set forth our meaning with perfect clearness, and the more subtle the misinterpretation, the greater the danger. The study and practice of argumentation is sure to reveal innumerable chances for confusion due to the lack of satisfactory definitions. We can seldom proceed far in any argument, no matter how simple it may seem to be, without feeling the necessity for this preliminary work of exposition. Without the protection of painstaking definitions, no point in an argument is proof against the insidious fallacies of ambiguity. When the two sides in a controversy use the same terms with different meanings or different terms with the same meaning; when colleagues are not agreed and consistent in the use of terms; when any man employs a term in one sense and later shifts to another sense, the result is a confusion which may carry in its train whole troops of fallacies. Clear and convincing definitions are fundamental requisites of sound argument.
Objectively and apart from our cognition, aspects of truth may, for aught we know, be diverse and multiform; in the infinity of space and time we have no adequate reason for affirming that they are not; but we cannot without the most gratuitous mental suicide allow the subjective co-existence of antagonistic convictions both claiming to be true at the same time. We must maintain, I think, the indivisibility of consciousness not only as an ultimate postulate of truth, but as a sine qua non of all affirmation and ratiocination of whatever kind. I am aware that this position — the ultimate veracity of consciousness, has been questioned; indeed, in a dialectical mood I have frequently questioned it myself, and in my own opinion not unsuccessfully so far as formal ratiocination is concerned. For that matter, I have had too long an experience of the subtleties and multiform aspects of logic not to know that there is no principle which can be formulated as an axiom of truth which unscrupulous dialectic cannot undermine. Even the ‘Cogito, ergo sum,’ of Descartes may be shown to be open to innumerable objections both as to form and substance. But while I think those extreme exercitations not only harmless in themselves but useful as intellectual gymnastics — just as the paradoxes of the higher mathematics may be useful — I nevertheless regard them as mere brutem fulmen when employed seriously to destroy consciousness: at most they can only result in setting reason to destroy reason — a mere self-stultifying and utterly ineffective operation. Reason and the direct deliverances of consciousness have a vitality much too inherent to succumb to attacks of formal logic, no matter how adroitly planned or how skilfully conducted. The dialectician who in earnest undertakes such a task is engaged in an enterprise much more fruitless than the ancient battle with the Hydra: the heads he amputates replace themselves with greater facility — the life he supposes himself to take is but the precursor of renewed vitality. From this standpoint of reason and consciousness we must, then, pronounce against all extreme forms of double-truth.
Shake off all fears and servile prejudices under which weak minds are severely crouched. Fix Reason firmly in her seat and call to her tribunal every fact, every opinion. Question with boldness even the existence of a God; because if there be one, he must more approve of the homage of reason rather than of blindfolded fear. You will naturally examine first, the religion of your own country. Read the Bible then as you would Livy or Tacitus. For example in the Book of Joshua we are told that the sun stood still for several hours. Were we to read that fact in Livy or Tacitus, we should class it with their showers of blood, speaking of statues, beasts, etc. But it is said that the writer of that book was inspired. Examine therefore, candidly, what evidence there is of his having been inspired. The pretension is entitled to your inquiry because millions believe it. On the other hand you are astronomer enough to know how contrary it is to the law of nature. … Do not be frightened from this inquiry by any fear of its consequences. If it ends in a belief that there is no God, you will find incitements to virtue in the comfort and pleasantness you will feel in its exercise, and the love of others which it will procure for you. If you find reason to believe there is a God, a consciousness that you are acting under his eye, and that he approves you will be a vast additional incitement: if that Jesus was also a God, you will be comforted by a belief of his aid and love. Your own reason is the only oracle given you by heaven; and you are answerable, not for the rightness but for the uprightness of the decision.
Were a man to abstract from every thing which he knows or has seen, he would be altogether incapable, merely from his own ideas, to determine what kind of scene the universe must be, or to give the preference to one state or situation of things above another. For as nothing which he clearly conceives, could be esteemed impossible or implying a contradiction, every chimera of his fancy would be upon an equal footing; nor could he assign any just reason, why he adheres to one idea or system, and rejects the others, which are equally possible.
Again; after he opens his eyes, and contemplates the world, as it really is, it would be impossible for him, at first, to assign the cause of any one event; much less, of the whole of things or of the universe. He might set his Fancy a rambling; and she might bring him in an infinite variety of reports and representations. These would all be possible; but being all equally possible, he would never, of himself, give a satisfactory account for his preferring one of them to the rest. Experience alone can point out to him the true cause of any phenomenon.