Satya or truth has been accorded the pride of place among the virtues recommended to be cultivated by man. The Hindu as well as Jaina and Buddhist works wax eloquently over it. Its fundamental definition is ‘that which is un-affected by time, place and causation’. This simply means that ‘satya’ stands for God, the Absolute. In fact, several sahasra-nāmas (thousand names of God) use this word to denote God. As an extension of this meaning, anything that helps a man’s progress towards God, is satya.
In a more practical sense, satya is speaking the truth, consonance of thought and word. One should avoid speaking falsehood, partial truths and even unpleasant truths. Truth should be spoken in a sweet and pleasant way. Unpleasant truths, when they must be spoken, should be presented in a palatable manner.
In the ancient days if a person accused of a crime denied it, he was to prove his innocence by touching a red-hot iron! It was believed that if he was speaking the truth, truth itself would protect him (vide Chāndogyopaniṣad 6.16.1,2)
Asatya on the other hand, stands for all that is opposed to satya. It is what is untrue, unreal, evil and crooked.
Speaking asatya has been permitted as an āpad-dharma (emergency situation), under extraordinary circumstances when one’s life is threatened by evil and unscrupulous persons.