Such a person has a natural ability to distinguish between right and wrong and his tendency is to do right. He was not dirty by birth but the society has made him dirty in beliefs and practices. Similarly, when beliefs and practices have become dirty, a purification job is in order and this purification is the entry into Islam through the door of witnessing or shahadah . Once a person has entered Islam he is purified as a newborn and has a second chance to start over again. His past sins are washed away while keeping his good works as assets.
Physical purification consists of purifying the body, clothes and environment.
The analogy of Islam is that of a building. A building has its foundation, pillars, roof, walls and other components. The pillars, walls, roof and other parts of a building are visible. Similarly, what a Muslim says and does is visible and become pillars, roof and walls of Islam. Frequently, Muslims talk about the five pillars of Islam without thinking that five pillars cannot stand without a foundation and only pillars standing on the ground are not called a building.