A condition encountered in the field of conditional logic that formalizes an intuition that any possible world $w$ is at least as similar to itself as it is any other. In semantics for conditional logics employing a system of spheres, this means that the world $w$ is a member of every nonempty sphere, i.e.,

• • For all $w$, if $S_i\in {\text{\$}}_w$ is nonempty, then $w\in S_i$.

When one employs distinct accessibility relation $R_{\phi }$ for each formula $\phi$, weak centring is formalized by the condition that:

• if $\phi$ is true at $w$ then $w{R}_{\phi }{w}^{\prime }$.

This condition can be strengthened to centring, corresponding to the demand that $w$ is the unique point more similar to itself than any other.