My position (as MysticMonist is already aware) is as follows:
One can know of God’s existence and His general attributes from reason alone. This is a major part of why the human intellect is reliable, however it is limited. Firstly, most people are slow to employ their reason. Secondly, one cannot attain detailed knowledge about God from reason alone. Thirdly, one cannot define good and evil from reason alone.
In all other fundamental matters as well, such as in law and order, commerce, healthcare, education, etc. when left to ourselves, we can only use trial and error without ever arriving at the best solution, and therefore we are in perpetual error when left to ourselves. However, God, being the creator of all things, has knowledge of all these things, which would include the best solution we are in need of. As God is under no obligation, it is not necessary for Him to solve our problems, for our actions neither harm nor benefit Him. However, it is necessary for us that God would commission a lawgiver/teacher who could impart divine knowledge rapidly and in a simple and concise manner.
The question then must be asked: Have we been abandoned to perpetual trial and error, or has God sent this lawgiver/teacher(s)? To answer this, we must be able to recognise who this lawgiver/teacher(s) is. Prior to being commissioned as lawgiver/teacher, this man must have a reputation among his people as having a truthful and upright character, otherwise how can we verify the claim to Prophecy of a treacherous liar as being true? This man must also be of high intelligence, to the point that He could grasp what is being revealed to him by God at once, otherwise how can we trust that an imbecile is correctly imparting to us the divine knowledge that was revealed to him, when he himself cannot grasp it? This man cannot teach what is contrary to what can be known in general by reason alone, namely the existence of God and His general attributes , otherwise how can we trust he is imparting the details of essential or fundamental knowledge, when he contradicts what is necessarily known in general? Finally, following all the aforementioned, he must affirm his Prophethood via an inimitable miracle. That is, an extraordinary break in nature, this would prove his Prophethood beyond doubt; for example, a king may send a man to some people, and after the people doubt that this man has been sent by the king, the man asks his king to stand up for him, which he does, proving that the man was indeed sent by the king.
We know from mutawatir (mass transmitted) evidence, that Muhammad (S) meets all of these criteria. Mutawatir evidence leaves no doubt in a narrated report. If 60 witnesses for example, heard one man saying “my favourite colour is black” and everyone without exception heard him make this statement, it is absurd to assert that not only did all of them mishear what the man actually said, but even more absurd to assert that they each heard the exact same thing from the moment they misheard the statement. The same would apply if a mass number of people witnessed one man doing something, and their testimonies of this man’s action are in agreement.