Falsehood can be defined as the absence of an accurate relationship between the true inner part of an entity and its superficial outer part.
Falsehood is the disparity between the actual and the appearance, between the thing itself and the outward impression that is formed.
Often, when people are called “liars,” “hypocrites,” or “deceivers,” these are people whose insides differ from their outsides.
One of the most basic falsehoods in the world is the falsehood inherent in social life.
Social life is only possible when people refrain from expressing their true feelings and opinions regarding others.
In practice, no society can exist at all without falsehoods.
Everyone understands the need for this type of falsehood: These are the structures by which society operates.
One does not share one’s every thought or opinion with everyone.
The Hebrew expression “derekh eretz” literally, “the way of the land,” refers to the concept of social politeness.
What people call “derekh eretz” is this whole institution of social falsehoods, which society is unfortunately unable to do without.
Such behavior includes showing respect even to those one does not respect, saying things that one does not mean when these are expected of him, and holding in things that one would like to say.
A look at how young children express themselves reveals that, often, their problems stem from the fact that their speech is uninhibited.
This is not to suggest that adults consciously and deliberately lie, but merely that they do not always tell the whole truth.
This is part of the system of social conventions. In this sense, falsehood can be thought of as a kind of garment that people wear, whose function is to conceal aspects of one’s self.
–Rabbi Adin Steinsaltz