In ancient Greek, the name for 'actor' in the sense of stage-player is 'hypocrites'. It is not widely appreciated that the basis of ordinary human social behavior is the playing of roles and the taking of parts, and that hypocrisy, whether mostly cynical, mostly sincere, mostly naive, mostly ironical, mostly conformistic, or mostly out of fear to be seen to deviate or to be abormal is what is best described as 'being social'. As William Hazlitt noted: 'No man is as much himself as when playing a part'.

The basic points here are two.

First, in all things human and social there is much room for hypocrisy of some kind, whether benevolent, as in politeness, or malevolent, as in deceit, and with many intermediate degrees that are difficult to distinguish clearly.

Second, this basic hypocrisy, this cant, this pretense, this acting as if, this role-playing, this deception and self-deception, this combination of collusion, delusion and illusion, is rarely faced fully, honestly and clearly, yet plays a fundamental role in human affairs, from friendship, love and marriage, to politics and religion.

1. Hypocrisy and cant: The distinction between hypocrisy and cant is both easy and difficult, since it is vague and fluent in practice, and much self-deception is based on a refusal to face evidence that goes against one's prejudices.

Both points may be illustrated by Hazlitt, who wrote a fine essay on the subject, namely 'On Cant and Hypocrisy'. First, there is the clear terminological distinction:

"He is a hypocrite who professes what he does not believe; not he who does not practice all he wishes or approves. (..) If anyone really despised what he affected outwardly to admire, this would be hypocrisy. If he affected to admire it a great deal more than he really did, this would be cant. Sincerity has to do with the connexion between our words and our thoughts, not between our belief and actions." 

Next, there is the loosening of terminology, though this may not be directly apparent:

"Thus, though I think there is very little downright hypocrisy in the world, I do think there is a great deal of cant - "cant religious, cant political, cant literary," etc. as Lord Byron said. Though few people have the face to set up for the very thing they in their hearts despise, we almost all want to be thought better than we are, and affect a  greater admiration or abhorrence of certain things than we really feel. Indeed, some degree of affectation is as necessary to the mind as dress is to the body; we must overact our parts in some measure, in order to produce any effect at all."

By contrast, I believe there is much hypocrisy in the world, but I agree with Hazlitt that since duplicity, dishonesty, insincerity and pretense are its basis, whereas its ends may be as varying as profit, safety or the advantages of another's love or liking, it is hard to fairly and precisely distinguish between all cases and kinds of hypocrisy, cant and deception.

In any case, I do not know of any prominent politician or religious leader who is not a consummate hypocrite - a successful flatterer, deceiver of and liar to his followers or flock, purportedly in their interests, but certainly in his own. And indeed, their excuse is valid, to some extent: One cannot lead a large group of people without lies and deception, for the average of a group is much below the average gifts of its individual members, and those who can and want to be lead in the mass must be led mostly by the nose, and by the stick and the carrot.

2. Personal and public character: There is a considerable difference, both in practice and in theory, between the personal character of humans, i.e. what they are and made of themselves, and show to their family, friends or themselves in private, and the public character of humans, i.e. what they show of themselves or of what they like to be seen as when performing some social role, whether this is work or connected to appearing in public.

There tends to be a considerable difference between these (sometimes charted in sociology or psychiatry under names like anomie and alienation), and a considerable hypocrisy in the common public character of humans. See: Character.