A condition sometimes imposed on models in conditional logic amounting to the claim that a world is more similar to itself than any other. In semantics for conditional logics employing a system of spheres, this is to say that for each possible world $w$, the set $\left\{w\right\}\in {\text{\$}}_w$, entailing that $w$ is a member of every sphere $S_i\in {\text{\$}}_w$. In semantics for conditional logics with a distinct accessibility relation $R_{\phi }$ for each formula $\phi$, this is formalized by the condition that:

if $\phi$ is true at $w$ then $w$ is the unique point $w^{\prime }$ such that $w{R}_{\phi }w\prime$.

This condition is related to that of weak centring, in which the condition is relaxed to the claim that each world $w$ is at least as similar to itself as any other.