In their recent Opinion article (Lymphocyte fate specification as a deterministic but highly plastic process. Nature Rev. Immunol. http://dx.doi.org/10.1038/nri3734 (2014))1, Reiner and Adams presented a fascinating deterministic interpretation of how lymphocytes acquire different fates. They propose that the generation of multiple lymphocyte subsets from each precursor occurs via an inevitable developmental pathway. This deduction is based on the premise that the system is too important to be left to stochastic processes. To account for recent evidence to the contrary, stochastic processes are suggested to only appear under conditions in which artificially large numbers of responding precursors might relax the deterministic programme (as used in Refs 2,3) or under in vitro conditions in which the usual three-dimensional (3D) arrangement of externally delivered signals that channel fates is removed (as used in Ref. 4). In other words, stochastic mechanisms only occur when experimental conditions happen to support the role of randomness.