in / priesthood

Re: in / priesthood
We all know that there are black sheep in every field and trade and even (in) priesthood.

1. Is 'in' optional or not needed?

"in" is definitly required.

2. Is 'priesthood' correctly used in the sentence?
No; "the priesthood" would be correct. remember about grouping singular things together? although there are many singular priests "preisthood" when considered as a whole becomes a single unit.
Therefore "the priesthood".

3, Can the sentence be phrased in a better way?

"We all know" .....do we? you are making an assumption about your audience that may not be true?

that there are black sheep

in every profession
in all walks of life

and even priesthood. "and" is not required here.



There are black sheep in all walks of life, even in the priesthood.

We can assume there are black sheep in all professions, even the priesthood.