[doodlebugging]

>We say B (and other Bodies alike circumstanced) are electrised positively; A negatively: Or rather B is electrised plus and A minus. And we daily in our Experiments electrise Bodies plus or minus as we think proper. These Terms we may use till your Philosophers give us better.

Sounds like he leaves it open for future "Philosophers" to update the convention as our understanding of the phenomena that he had documented improved. Smart guy in not assuming that he got it right the first time. Franklin sounds like he wasn't a "my way or the highway" type of guy.