Many philosophers have torn holes in rational proofs of God made by Descartes, Anselm, Augustine, etc., so much so that even religious philosophers such as myself rarely use their proofs. However, as far as I am aware, no one has ever been able to disprove or even discredit Thomas Aquinas' proofs of God's existence, which are scientific in nature. I think that a skeptic in the tradition of David Hume could easily do so, however in my experience most modern atheists are not skeptics but scientists (you cannot be a skeptic and a scientist). I cannot comprehend how an intellectually honest scientist could read Aquinas' proof and not confess that God must exist.
For those of you not familiar with his proofs here is the full text:
http://www.braungardt.com/Theology/P...as_aquinas.htm
The 4th and 5th proofs are a little too Aristotelian I think and different than the first three, so I would rather keep this discussion to the first 3 proofs are very relevant.
1.The first and most obvious way is based on the existence of motion. It is certain and in fact evident to our senses that some things in the world are moved. Everything that is moved, however, is moved by something else, for a thing cannot be moved unless that movement is potentially within it. A thing moves something else insofar as it actually exists, for to move something is simply to actualize what is potentially within that thing. Something can be led thus from potentiality to actuality only by something else which is already actualized. For example, a fire, which is actually hot, causes the change or motion whereby wood, which is potentially hot, becomes actually hot. Now it is impossible that something should be potentially and actually the same thing at the same time, although it could be potentially and actually different things. For example, what is actually hot cannot at the same moment be actually cold, although it can be actually hot and potentially cold. Therefore it is impossible that a thing could move itself, for that would involve simultaneously moving and being moved in the same respect. Thus whatever is moved must be moved by something, else, etc. This cannot go on to infinity, however, for if it did there would be no first mover and consequently no other movers, because these other movers are such only insofar as they are moved by a first mover. For example, a stick moves only because it is moved by the hand. Thus it is necessary to proceed back to some prime mover which is moved by nothing else, and this is what everyone means by "God."
Aquinas predates Newton by a couple of hundred years, but it seems to me this is a logical and obvious conclusion of Newtons laws of physics.
2. The second way is based on the existence of efficient causality. We see in the world around us that there is an order of efficient causes. Nor is it ever found (in fact it is impossible) that something is its own efficient cause. If it were, it would be prior to itself, which is impossible. Nevertheless, the order of efficient causes cannot proceed to infinity, for in any such order the first is cause of the middle (whether one or many) and the middle of the last. Without the cause, the effect does not follow. Thus, if the first cause did not exist, neither would the middle and last causes in the sequence. If, however, there were an infinite regression of efficient causes, there would be no first efficient cause and therefore no middle causes or final effects, which is obviously not the case. Thus it is necessary to posit some first efficient cause, which everyone calls "God."
Again, seems to me obvious to anyone with an understanding of causality, which always makes me wonder how so many scientists can be atheists (in that science is based on causality
3. The third way is based on possibility and necessity. We find that some things can either exist or not exist, for we find them springing up and then disappearing, thus sometimes existing and sometimes not. It is impossible, however, that everything should be such, for what can possibly not exist does not do so at some time. If it is possible for every particular thing not to exist, there must have been a time when nothing at all existed. If this were true, however, then nothing would exist now, for something that does not exist can begin to do so only through something that already exists. If, therefore, there had been a time when nothing existed, then nothing could ever have begun to exist, and thus there would be nothing now, which is clearly false. Therefore all beings cannot be merely possible. There must be one being which is necessary. Any necessary being, however, either has or does not have something else as the cause of its necessity. If the former, then there cannot be an infinite series of such causes, any more than there can be an infinite series of efficient causes, as we have seen. Thus we must to posit the existence of something which is necessary and owes its necessity to no cause outside itself. That is what everyone calls "God."
The first two proofs prove that there must be a creator (God). The third one proves he has no cause, i.e. he is eternal. For those of you interested, the 4th proves he is perfection and goodness, the 5th that he is still a controlling force in the world (however, as I said Id rather just discuss the first three).