The key-point of this article is the theory of 'qabz va bast-e teurik-e shari'at' (The theory of expansion and contraction of religion) developed by Abdolkarim Soroush, one of the most famous and highly regarded contemporary Iranian intellectuals. His theory is centred around the issue of variability of our perception of the world and religion. Soroush calls for constant interpretation of the sacred texts and insists on perceiving knowledge as a process of permanent contractions and expansions (qabz va bast). By using these concepts he refers to Sufism, where both terms are often applied to describe mystical states of the disciple. The analysis of the terms 'qabz' and 'bast' makes it possible to place his theory in the context of a much broader problem, that is to say the dynamic nature of the world. It allows one to demonstrate that the idea of constant change which leads to development, found in Sufi poetry and in philosophical teachings of some Persian philosophers, is still present in human culture and consciousness regardless of the passing centuries.