to prove that the qur’an is the word of allah, you do not have to indulge into futile discussions or philosophical dialect. you have at your disposal a “living material evidence,” the qur’an itself. starting with the null hypothesis, i.e., assuming that the qur’an is not the word of god, one should ask himself: could a human being in the seventh century write such a book? or does there exist—up till today—any book that is claimed to match the qur’an?
let us examine the qur’an more closely. starting with the content, could the knowledge therein have been within the reach of any human source, i.e., the prophet muhammad, his contemporaries, or the whole human civilization and for several centuries ahead? how could a book revealed at that point of history refer —in precise terms—to scientific phenomena and historical events—prior and subsequent—that were unknown or misunderstood before their subsequent verification?
these qur’anic references cover such wide spectrum of topics as the nature of space, relativity of time, the shape and motion of the earth, the role of mountains, water for life, the water cycle, the sources of rivers and groundwater, sea depths, embryology, hygiene and proper health practices, prophecies fulfilled (after revelation), etc.
as to the form of the qur’an—i.e., linguistic and literary features—any strict comparative analysis identifies the qur’an to be not only superior to any other text—preceding or following, including the sayings of the prophet himself, who received and delivered the revelation—but also to be a perfect, flawless and the most eloquent composition. this perfection can be witnessed and proved on the levels of the individual words (semantics), sentence (grammar and rhetoric), and whole surahs (chapters).
thorough examination of the qur’an shows that each of these elements was selected and phrased in the most appropriate manner to fulfill the most precise meaning and most effective impact, whether cognitive, psychological, passionate, or phonic, on the reader or listener. the qur’an challenges mankind, arabs and non-arabs, to the end of time, to produce anything like or compared to itself. and so it is proved.
all that said can in itself be enough to answer your second question as to the existence of allah almighty. if the qur’an is the true undisputed word of allah, then it follows that whatever is in it is the absolute unquestionable truth.
over the millennia, philosophers’ attempts to agree, through abstract arguments alone, on the existence of god, his attributes, and the way he interacts with his creatures, have all been futile. the human mind can only observe, measure, compare, correlate, and hence theorize, within the limited capacities created in man, and no more.
our senses have limits. for example, we can see only those bodies emanating light in the wavelength range of 0.4 to 0.7 microns, and can hear only those sounds in the frequency range of 2500 to 4000 cycle per second. in time and space our perception is limited by the velocity of light, since the visible universe is so wide as to be measured in billions of light years. this means that what we will ever see—however advanced our technology is—are only images from the far-deep past. also, what we can see is essentially no more than an extremely minute fraction of the real existence.
we can know allah as the creator and sustainer of this universe through his detectable creation. the harmonious “intelligent” physical systems in our bodies and other biological species (plant or animal), in matter in general (viewed at the sub-atomic or cosmic levels) boldly manifest the purposeful design, endless diversity, and sustainable precise running of all these systems. allah only is the one god who can consistently create and sustain such a marvelous, harmonious universe like this. praise be to him!
abstract philosophical thinking alone could never and can never conclusively prove or disprove the presence and attributes of god. proving the existence of god is and should always be beyond the reach of human philosophy. philosophy cannot—in itself—produce or create knowledge, but only through concrete observations together with sensible percepts can it offer any sound conclusion.