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Judging politicians by their speeches is the equivalent of judging cars by their salesmen.
Among preachers and orators of all kinds, we can differentiate four types:
Cunning: we are all too familiar with this type of politicians and sales people. They will try to promote and sell products, ideas or candidates using argumentations that they know not to be true or at least a sufficiently distorted version of reality in order to make it palatable to a gullible public. We live in a society where lying has been elevated to an art form. The lying is so constant that it has stopped being shocking and is now often being accepted, especially in commercial advertising.
Mistaken: they are sincere and really believe in what they say... but ultimately, they are wrong!
Interested: those are the sales people and the motivational speakers who may very well believe in the vaunted qualities of their products and ideas but who also have to directly gain from their public also believing the same, in terms of product sales, book sales, or votes gained.
Hypocritical: also known as the people who say: "Don't do as I do but do as I say!". They are good-natured, well-intentioned people who are unable to live the message that they preach but who expect other people to ("for their own good" or "for the good of the society"). They have nothing to gain from you but they basically want you to change the world for them, by doing things that they themselves cannot do.
Knowledgeable: those are the people who do not limit themselves to regurgitating talking points. They know the issue, studied the details, have an in-depth knowledge of the facts.
Inspiring: those are the people who intimately believe in what they say and actually live according to their beliefs. They are living examples, truly inspiring role models that we can look up to.
In life, it helps to remain aware of which category the people we meet and listen to belong to, whether we see them on our TV screens or at our kitchen tables.