Be "The" Expert

How often do we phrase: "We need an expert to do this or that"?

Why don't YOU be THE expert to be called on when your expertise is needed.

Seth Godin refers to an article in Times and writes:

"For the past couple of years Jun Kaneko, the ceramic artist..."
It didn't say "a ceramic artist." No. It said, "the ceramic artist".
The entire tone of the piece changes. It's so much better to be a 'the' not an 'a'.

What about you? Are you the expert?