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The PYTHIA Monte Carlo (PMC) has been applied broadly to simulations ofhigh-energy $p$-$p$ and $p$-$\bar p$ collisions. The PMC is based on severalassumptions, such as that most hadrons result from jet production (multipleparton interactions or MPIs), that $p$-$p$ centrality is relevant and thatcolor reconnection (CR) strongly influences fragmentation to jets. Analternative description is provided by the two-component (soft + hard) model(TCM) of hadron production. TCM analysis of $p$-Pb ensemble-mean-$p_t$ datareveals centrality trends quite different from those estimated via a geometricGlauber model based on the eikonal approximation. Glauber estimates ofbinary-collision number are three times TCM estimates. Detailed study of $p$-Pbdata conflicts with a basic Glauber assumption -- that a projectile proton mayinteract simultaneously with multiple target nucleons. Instead, in both $p$-$p$and $p$-A collisions, a $p$-N collision once initiated is exclusive of otherpossible interactions (during that collision), and within the collision anypair of participant partons may interact -- a $p$-N collision is thus "all ornothing." In this presentation the PMC is challenged by an assortment ofcontradictory data, and evidence for $p$-N exclusivity is reviewed to make acase for the "preoccupied proton" of the title.

PYTHIA and the preoccupied proton