Who is Allah?

The reason that things must have a creator, is because the things which are comprehensible by the mind that is man, life, and the universe, are limited, weak, imperfect, and are in need for something other than themselves. Man is limited, because he grows in every aspect to a certain limit that he cannot surpass, so he is limited. Life is limited, because it manifests itself only in individuals, and what is noticed by the senses is that it is concluded with the individual, thus it is limited. The universe is limited, because it is the sum of celestial bodies, and each body is limited; and the sum of limited things is self-evidently limited. Thus, man, life, and the universe are definitely limited. When we ponder on the limited (thing), we see that it is not azali (eternal - limitless), otherwise it would not have been limited, and therefore, it must be created by something else, which is the Creator of man, life and the universe. This Creator, is either created by someone else, creator of himself, or azali (eternal - limitless) whose existence is indispensable (wajib ul-wujood). It is absolutely false that he is created by someone else, because he would then be limited. It is also false that he is the creator of himself and could not be rationally considered as the Creator. As for being self-created, the ramification of which would be he is created by himself and creating himself simultaneously. This is simply absurd. Hence, the creator must be azali(eternal - limitless) whose existence is indispensable. He is Allah.

~ An Excerpt from The System of Islam (English translation of Nidham-ul-Islam by Taqi-ud-Din Nibhani)

P.S. Although I believe that Allah does not has a gender, but one has to use some keyword while writing. As in normal writing, the word 'He' is used here, and I had to go with it.