What is your definition of truth?
Truth is defined as something that is ‘faithful’ to a true source. This idea is expressed in the word EMET, which is made up of the letters aleph, mem, taf — the first, middle, and last letters of the Hebew alphabet (Gemara Shabbos 104, and in greater detail in the Midrash). This means that the word plots a straight line from a first source (the aleph), through the middle (mem), and to the final revelation (tav). When the final revelation is true — faithful — to its initial source, plotting a straight line from the source to the revelation, then it is true.
On a simple level, a statement of fact is therefore true if it is based on true facts. On a deeper level, even our thoughts and deeds are ‘true,’ if they derive from a source of an elevated, spiritual truth. This is the idea of keeping the Torah, which raises our deeds to the level of spiritual truth, for by means of the Torah, all of our deeds are derived from the spiritual reality of the word of God.
For this reason, it is sometimes permitted to tell a lie. If the lie is mandated by the cirsumstances, for example, it is required in order to bring peace, then based on the above definition, the lie itself is considered ‘truth’.
The Midrash states that when Hashem created the world, He hurled Truth to the ground, and stated: Truth should arise from the earth. It is our duty to make all of our deeds and ways expressions of an elevated truth, so that truth will rise up from the earth.