Mentally he promised himself that he would never again use a collar on any living creature.
mentally
/ˈmen-tᵊl-ē/
adverb
in the mind : using the mind
with regard to the mind or its capacity
adjective
of or relating to the chin : genial
adjective
affected by intellectual disability : intellectually, disabled
… Rosa's Law, which changed references in federal law from "mental retardation" to "intellectual disability" and references to a mentally retarded individual to an individual with an intellectual disability.