I believe the term 'heart' when used in this context means 'core', as in 'the heart of the matter' or 'the heart of the organisation' though the fact 'heart' is used to mean 'core' is because people did literally believe the heart was the organ responsible for emotion, not the brain,(which was used for logic, which isoh so totally separate from emotion)
which is now recognised as our 'core', the heart of all out biological functions.
I believe the term 'heart' when used in this context means 'core', as in 'the heart of the matter' or 'the heart of the organisation' though the fact 'heart' is used to mean 'core' is because people did literally believe the heart was the organ responsible for emotion, not the brain,(which was used for logic, which isoh so totally separate from emotion) which is now recognised as our 'core', the heart of all out biological functions.