Expertise merely refers to one’s knowledge or skill in a particular field, but my understanding of CPR or ability to bake shortbread cookies does not make me an authority over you. Other than the conflation of force and authority, this is one of the most common confusions people have about anarchism, made worse by the fact that there are some anarchists who still use authority to refer to both command and expertise just because Bakunin did. Personally, I find that creates needless confusion. If you’re using the word authority to describe everything from slavery to knowing how to build a bridge, then why use the word at all? Just use the word expertise when you’re talking about expertise. Listening to medical advice isn’t a hierarchy. Having expertise doesn’t give me the right to command you unless I hold a position in a hierarchical power structure that grants me that authority. As Bakunin himself said:
…we ask nothing better than to see men endowed with great knowledge, great experience, great minds, and, above all, great hearts, exert over us a natural and legitimate influence, freely accepted and never imposed in the name of any official authority whatsoever, celestial or terrestrial.