The idea of tying social rights to social participation indeed comes with one major caveat: it may be hard to implement. Atkinson did not give a precise rule to define the forms of contributions that entitle people to receive participation. That gives the idea a general character with a large variety of practical application. Meanwhile, it also leaves the idea vulnerable to criticism. The philosophical grounds against the reciprocity norm are not as solid as the administrative critique of Atkinson's original idea of participation income. The discussion on whether UBI fulfils the reciprocity norm, and if not, could PI fulfil it is still undecided among political philosophers. An important argument also concerns inequality. It is not reasonable to enforce reciprocity norm in radically unfair societies. If PI is understood as an alternative to UBI with the aim of covering the whole or nearly the whole population, administrative challenges are imminent.