The problem of irreversibility was raised in the second half of the 19th century in thermodynamics and, a few years later, in evolutionary biology. In the 1970s, economists accounted for the problem of irreversibility in the context of human-driven ecological change. Social theory missed the problem – with regard to social reality it did not receive any attention. This paper seeks to fill the gap. In order to do so irreversibility has to be redefined. In physics and life sciences it is conceived as a property of a process. In this paper, irreversibility is defined as a social situation wherein one reality is bound to disappear without any chance of recovery and another reality to emerge in its stead. Social situations of irreversibility are further classified into anoetic, rational, and ethical with each type discussed separately. The concluding section addresses formative conditions of respective situations of irreversibility, types of experience, and limitations of descriptive language.