Who said "The greatest deception is self-deception"?

This quote is attributed to Dr. John Watson.

The greatest deception is self-deception - Dr. John Watson

"The greatest deception is self-deception"

Dr. John Watson Truth

Character in The Hound of the Baskervilles

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"I am not a very good subject for a novelist."

"The greatest happiness the greatest number."

"We are not beaten yet."

"Justice, however delayed, is not denied."

"Lucy, you got some 'splainin' to do!"

"You must always be honest with the people you love."

"Truth always comes out in the end."

"Honesty is always the best policy."