One of the reasons Islam appeals to some people is because of the vaunted simplicity of its conception of Allah, i.e. what Muslims call tawheed or Allah’s absolute oneness. This most important part of the Islamic creed (aqidah) is supposedly so simple that even a child can understand it.
Contrast this with the doctrine of the Trinity, the teaching that God is tri-personal. In some ways this doctrine is so abstruse and mysterious that even the most powerful intellects throughout history have had great difficulty and no success in completely wrapping their minds around it.
While the simplicity of tawheed can be called into serious question, for arguments sake and for the sake of the following observations, this otherwise dubious claim may be granted.
Assuming, then, that Allah is so effortlessly apprehensible and comprehensible that juveniles can understand him, and that with the kind of ease they understand other things in ordinary, everyday human experience, how is this supportive of the conclusion that Allah is the God who made heaven and earth rather than unsupportive of it? Doesn’t this observation really impinge on such a conclusion? That Allah would no more tax our mental powers than other created things that are amenable to man’s limited noetic faculties is surely problematic. In fact, while there are things in human experience or creation that are relatively easy to understand, there are also a great many realities and factualities that are not. Since some things in human experience or creation transcend comprehensive rational scrutiny, Allah would not only be on the level of the multitude of created things which our minds can penetrate; he would even be beneath those created things which our minds have not been able to get to the bottom of. If Allah does not boggle our minds, then he can hardly be the creator and maker of the apparently limitless but yet still finite universe that continues to stupefy the world’s brightest intellects. All of this suggests, nay, strongly argues for the fact that Allah is a product of a/the human mind instead of being the one who made the complex world of men and things. A god who fits neatly into our creaturely categories of understanding loses all claims to be the one who is the transcendent ground and source of all things. Water can’t rise higher than its source, and an effect can’t be greater than its cause.