Assalamu alaykum. Today a lot of Muslims commit major acts of shirk without even realising it. It has been said about the Quraish that they understood shirk better than us, because while they worshipped Allah they knew they associated others with Him (swt) through idolatry. There are 3 aspects to tawheed: Rububiyah, Asma was-Sifat and Al-Ibadah. Shirk committed within Rububiyah are of two types: 1. Shirk by association: this means directly assigning other gods, people or objects with attributes of Allah. For example, in Hinduism there is Brahma which created all things and which everyone goes back to and then there is Brahma the god who shares trinity with Shiva (destroyer god) and Vishnu (preserver). 2. Shirk by negation: this means to deny the existence of Allah either explicitly or implicitly. An example of explicit denial is atheism, while implicity denial is pantheism. Buddhism is an explicit example. Darwinism and evolutionism, and many other European philosophies and concepts are also explicit denial, as they show god being the fabrication of man (such as in Marxism). Implicit denial can be seen in some Sufi sects, such as the concept of Ibn 'Arabi, who say God is everything and everywhere, which means all things even the human are made up of God. This similar to concepts of Hinduism. It is clear from the Qur'an that Allah is 'up' and 'above the heavens'. An example of this is miraj made by Muhammad (saw), as he went up through the heavens to speak with Allah.