Article 12.5 of the Kyoto Protocol specifies that emission reductions are only to be certified under the Clean Development Mechanism (CDM) if they are additional to any that would occur in the absence of the certified project activity. The primary question to be pursued in this discussion paper is simply: Why? What are the reasons for imposing such a restriction on what activities are to be admitted under the CDM? The aim of this exercise is, in a first instance, to get a better understanding of what this additionality condition is meant to achieve, and secondly to have either clearer ideas of ways in which it might be improved to achieve this stated aim, or clearer arguments as to why it should be rejected. Some of the arguments that can be put forward for the use of additionality will be listed at the end of this section.