Bass Players...A question of some debate.

While I was at a music store this weekend buying my new Fender Jass bass, I overheard the salesman telling a new player that the bass is always played with the fingers never a pick. I naturally stepped in and spoke my two cents (which is what I had left after my purchase...)

I told the salesman that I mostly use a pick when I play bass as does Carol Kaye and thousands of other great players. First he asked "Who is Carol Kaye???"

What about this notion of the pick?

Some players use their thumb, players like the Late, Great James Jamerson used his index finger only and some use a pick.

What is your preference and why?