• Active-Inert Factorisation. Every morphism of pointed sets $f\colon \webleft (X,x_{0}\webright )\to \webleft (Y,y_{0}\webright )$ factors uniquely as
    \[ f=a\circ i, \]

    where:

    1. The map $i\colon \webleft (X,x_{0}\webright )\to \webleft (K,k_{0}\webright )$ is an inert morphism of pointed sets
    2. The map $a\colon \webleft (K,k_{0}\webright )\to \webleft (Y,y_{0}\webright )$ is an active morphism of pointed sets.

    Moreover, this determines an orthogonal factorisation system in $\mathsf{Sets}_{*}$.


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