When asked, "What is a lie?" Augustine responded: "Any statement meant to deceive another." And he also said, "No lie is ever justified for it sets up a dichotomy between what we say and what is in our hearts."
I would say that I am a very open and honest person, and that I put a very high value on honesty and sincerity. I absolutely despise liars and cheaters, brown nosers and backstabbers, people who will say or do anything to get ahead, when it is at odds with what is in their own hearts.
But honesty is not always kind or pleasant. A person could be brutally honest. A person could be cruel and disrespectful and hateful, while at the same time being completely honest about it. So honesty is not necessarily kind or noble, but it is clear and direct, where you at least know that whether you like it or not, what you see is what you get.
Making your intentions clear from the beginning, saves a lot of trouble later down the road. Dishonesty causes many problems in relationships of all kinds, and is a major reason why I think marriages fail, because people were not being completely honest about things from the start, perhaps trying to be someone their not in order to impress the other, or by trying to force an unsuitable relationship to work. But that only works for so long, eventually the real you is going to make an appearance, and it may not be to the other person's liking.
So it is better to be honest from the start. At least you know where a person stands, and you can decide whether you wish to stand with them, or apart from them, to stand for them or against them.
I'm a strong believer in saying what you mean and meaning what you say. If you are honest, there is clearer communication, and less likely to be misunderstandings. You may not like what you see, there may be disharmony and disagreement, but at least you'll know what you are up against, and be less likely to end up wasting energy in counter productive relationships (whether business or pleasure) with people you are not compatible with or who have conflicting objectives.
Why do people lie? Many reasons, but mostly to get what they want, when telling the truth would fail to do so.
Sometimes people may lie due to a personal weakness, perhaps out of cowardice. They are afraid of owning up to the truth, so they find it easier to lie in order to avoid having to taking responsibility for their actions, or having to face conflicts and hardships or unfavorable outcomes.
Other people lie for more devious purposes, not because they are personally afraid, but in order to exploit other people's fears and weaknesses. People lie to control others, to get people to do what they want them to do, when telling the truth would not achieve those ends.
But a lie is doomed to fail from the start, because just like the sunshine, the truth has a way of coming out, and dispelling the darkness of confusion and falsehood, while bringing the truth into the light day.
The sun is a perfect symbol for truth: light, illumination, clarity, perception, understanding. A lie on the other hand, is more aligned with darkness, misunderstanding, confusion, deception, ignorance, and falsehood.