What Is Kant's Duty To Lie

It seems that Kant has a much more conservative view towards lying and when it is permissible. Grotius has a much more liberal, modern, and understanding view on the issue. Kant pretty much thinks that it is one's duty to speak the truth, although this moral principle is not taken unconditionally in the world today. This is a duty because it is every man's right to know the truth and lying to anyone would be taking this right away, which mortals should not have the power to do. However, if a man throws this right away, through committing evil acts that are opposed to the good of mankind, he no longer has a right to the truth and he can be lied to. Also, if a one forces another man to speak, the man has no duty to tell the truth, because
the truth is not supposed to be obtained in this way. Some believe that lying does not count if it does not injure another person directly, however Kant believes that lying always hurts mankind generally, and is therefore unjust. Even if one lies to a murderer to try to prevent another man's death, the consequences might be other than expected and one might be held responsible for these consequences by law, even if they were not intended.
Grotius believes that if a falsehood is unpermissible, it is in direct violation with the right of another person. However Grotius has a list of falsehoods that are permissible. These include: lying to an infant or insane person, deceiving someone who one is not specifically addressing, deceiving someone for their own good, deceiving someone if in power and looking out for the common good, lying when there is no other way to save an innocent life, and lying to enemies. This last one is permissible, but not noble and therefore some may want to refrain from it. These permissible lies are not extended for promises or oaths, however, because those are judged by different standards.