not disposition

[kingston_123]

Mcqueen says to Hercule Poirot about him:

Prohibition wasn't to my taste...so I found myself overseas, and in debt. I'm a lawyer by education...not disposition. I was downright awful at it.

Why is there no article before "disposition"?
Source: Murder on the Orient Express (2017) Film
Screenplay by Michael Green
Based on "Murder on the Orient Express" by Agatha Christie.

 

[J&K Tutoring]

Perhaps filling in the 'missing' parts might help:

I'm a lawyer by education.​

I'm not a lawyer by disposition.

 

[heseinfathi]

"I'm a lawyer by education...not disposition."
I was wondering what the statement means. I could figure as much as there are two paths to becoming a lawyer; the academic path (by education), and by disposition. Does 'by disposition' mean something similar to being an apprentice to a seasoned lawyer and picking up the profession by observation and practice (no academic education)? Or does it mean he did not like the study of law but he ended up being one just because he studied it?

Thank you in advance.

 

[SoothingDave]

No, he means he has the education for it, but does not have the right mentality/personality/mindset for being a lawyer.