"For if we know how to prove the truth, we shall know at the same time how to distinguish it from error."
This quote sounds like something we might read from the philosophers Aristotle, St. Thomas Aquinas, or even the apostle Paul. However, this is actually a quote from the introduction of Pascal's Treatise "On Geometrical Demonstration", in which Pascal discusses the methods of proving the truths in geometry. Read the quote again, is any other defense necessary for why we teach our children logic, debate, and geometry?
Identifying the truth is important, but often the truth is masked in a world of confusion. Messages like "God helps those who help themselves" and "you can do anything you set your mind to" sound simply appealing, but are they true? How do you know when something is true?
In a classical education, we don't simply teach our children what is true, good, and beautiful, but we show them how to determine when something is true, good, and beautiful.
In logic, we don't merely study the meaning behind the famous syllogisms, but we practice testing syllogisms for validity.
In debate, we don't learn how to persuade for the simple art of persuasion, but so that we can seek out the truth together, with our opponent, not against. Our common goal is to know the truth.
In geometry, we study the patterns for determining the congruence of triangles not because we will encounter many triangles in our lives, but because we will encounter many false statements masked as truths. Learning how to "see" the patterns in the triangles helps us know how to "see" the pattern of truth in life.
There's more to your child's education than simply building skill with a compass. Knowing how to distinguish truth from error is a much greater goal.