Discussion Hall

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pro Theism                                              onlookers                                                            pro Atheism

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Theist: Presentation #1: That the Existence of God is demonstrable by reason To prove the thesis it is first necessary to explain what a philosophic demonstration is. A philosophic demonstration is a manifestation of reasons or evidence adduced in favor of a conclusion based on a reflecion of the nature of the subject examined. Now demonstration of this kind can be made in two ways: "a priori" and "a posteriori". A demonstration "a priori" can be termed a mathematical kind of proof. It necessarily concludes and forces the assent of the reason to the conclusion, for "a priori" terms. For example, the demonstration of 1+1=2 depends absolutely upon the definition of the terms of "1" "+" "=" and "2". This is to argue from an "a priori" cause(s) to an effect. A demonstration "a posteriori," on the other hand, proceeds from the effect to the cause(s), the effect being more certain or clearly known, the existence and or nature of its cause is concluded. For example, smoke is observed comming from a certain place, and the existence of a combustible reaction is demonstrated from this effect. Hence it follows from the nature of a philosophical demonstration "a posteriori" that any observed effect whose existence cannot be but through the postulation of the existence of a cause, demonstrates reasonably that such a cause exists. Now it is clear that the validity of the demonstration "a posteriori" depends only on two things, namely, the existence of the effect, and the necessity of relation between cause and effect. It is also clear that such a line of argumentation does not conclude to any perfect knowledge of the essence of the cause, but merely that is does exist and has a nature sufficient to cause the effect. Thus far, the nature of a philosophic demonstration. Now to conclude to the proof of the thesis. I. If there is a God who is a cause of something knowable, then the existence of this God is demonstrable "a posteriori". II. If there is a God whose essence is knowable, then the existence of this God is demonstrable "a priori". These follow from the nature of the two kinds of philosophic demonstration. For in the first case, God is a cause of a known effect, and in the second, the nature of God is presupposed as a definition. Examining the first case, more closely: III. If there is an effect, the cause of which cannot be but by postulating the existence of God, then such an effect demonstrates the existence of God. and, likewise, the the second, more closely: IV. If there is an idea of God that necessarily includes existence, then such an idea demonstrates the existence of God, necessarily. However, the fourth statement, is argued by some to conclude only in the order of ideas of existents and not of existing-existents, and therefore is rejected by some as an invalid or insufficient. Nevertheless, the third statement, concludes validly on the condition stated therein. Hence, the existence of God is demonstrable by reason, if the third statment is validly demonstrated. (cf. Is God's Existence Demonstrable , by Thomas Aquinas)

Mike Hardie: Call-for Clarification Firstly, I agree with your basic introductory info. I'd just like to add that some people might be more familiar with the terms "a priori" and "a posteriori" truths as analytic and synthetic truths respectively. Indeed, if an effect is proven existent, and proven to be only causable by God, then God is proven to exist (your part III). Now, if an idea can be shown to exist, and it can be shown that this idea is only causable by God, then an idea can suffice to prove God's existence -- if this is all you mean to claim by IV, then I agree there again. However, if you intend by IV to establish that something along the lines of Anselm's Ontological Argument validly proves God's existence, then I definitely disagree. Anselm's argument, for the benefit of those not familiar with it, attempted to prove that God must exist by stating that the definition of God necessarily required that He be existent. Specifically, the quality "perfect" was seen to indicate existence, because Anselm deemed it greater to exist outside the mind (i.e., in objective reality) than within it (i.e., as merely a mental concept). The problem, however, is that this same reality / concept distinction negates the Ontological Argument. Anselm can say that "God, by definition, exists"; but to conclude from this that God actually exists is to assume that something exists in reality that meets his definition. Since only God meets the definition of God, this, in turn, means assuming that God exists.... but this is what the whole argument is trying to prove! This makes the Ontological Argument guilty of the fallacy petitio principii (or begging the question), because it necessarily takes its conclusion as an implicit premise. All Anselm could really validly conclude from his argumentation is the hypothetical "if God exists, He exists", which is a decidedly unnecessary point. Theist did appear to make note of this sort of objection to IV, but I felt it necessary to elucidate my position here nonetheless, if only for the sake of clarity.