There are deep underlying similarities between Rosen's (M,R) systems as a definition of life and the RAF sets (Reflexive Autocatalytic systems generated by a Food source) introduced by Hordijk and Steel as a way of analyzing autocatalytic sets of reactions. Using RAF concepts we have systematically explored the set of possible small idealized metabolic networks, searching for instances of (M,R) systems. This exhaustive search has shown that the central requirement of Rosen's framework, unicity of Φ, becomes harder and harder to obtain as the network grows in size. In addition, we give an expression for operators f, Φ and β in terms of RAF sets.