What is conscience?

A ray of thought can benefit or injure the person it is directed towards. 

If it is a good thought, it benefits him by bringing him into rapport with the thinker who may be a good man—

By this means, he is benefitted, and is analogous to the pleasurable feeling, which you experience when you hear yourself praised or receive a kind word from a friend or a kind letter. 

These are the spiritual benefits, which benefit the bodily health of the recipient by raising his hope and confidence in himself—

In other words, his self-satisfaction, which is only another name for the approval of his conscience. 

Conscience is merely each one's standard of right and wrong. 

Though there is a certain uniformity in your notions of right and wrong, yet some conceive to be right what others would very much question. 

The former's conscience is more easily satisfied than the latter's. 

Practically, each attains the same end, viz., the satisfaction of his conscience. 

It does not, however, follow that either will attain happiness because both may have erroneous standards of right and wrong, and each one's standard of right and wrong is the measure of his wisdom and spiritual development.