E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Have you the conscience to [demand such a price]. Can your conscience allow you to [demand such a price]. Conscience is the secret monitor within man which accuses or excuses him, as he does what he thinks to be wrong or right.
In all conscience. As, And enough too, in all conscience. Meaning that the demand made is as much as conscience would tolerate without accusing the person of actual dishonesty; to the verge of that fine line which separates honesty from dishonesty.
My conscience! An oath. I swear by my conscience.
Court of Conscience. Established for the recovery of small debts in London and other trading places. These courts have been superseded by county courts.