Is a secular person an infidel?

Secularism is irreligion or worldliness; it calls for the establishment of life away from religion. So, whoever believes that Islamic Sharia (definition) is not suitable for worldly affairs, or that it was suitable for a period then times changed, or that it does not align with civilization and calls for backwardness, is to be taught and have the argument established against them. If they repent and believe in the suitability of Islam, then that is good; otherwise, their disbelief and apostasy are confirmed, even if they pray and fast and claim to be Muslim. Allah Almighty says: "O you who have believed, enter into Islam completely [and perfectly] and do not follow the footsteps of Satan" (Al-Baqarah:208), and He says: "He has ordained for you of religion what He enjoined upon Noah and that which We have revealed to you, [O Muhammad], and what We enjoined upon Abraham and Moses and Jesus - to establish the religion and not be divided therein" (Ash-Shura:13), and He says: "And whoever seeks a religion other than Islam, it will never be accepted of him, and in the Hereafter he will be one of the losers" (Al Imran:85). Religion is a system of life that includes acts of worship, conduct, transactions, and beliefs. The servant must obey Allah's commands and prohibitions, because the Creator knows best what benefits him. Allah Almighty says: "Does He who created not know, while He is the Subtle, the Acquainted?" (Al-Mulk:14).