Freethinkers are naturalistic. Truth is the degree to which a statement corresponds with reality. Reality is limited to that which is directly perceivable through our natural senses or indirectly ascertained through the proper use of reason. Reason is a tool of critical thought that limits the truth of a statement according to the strict tests of the scientific method. There is no great mystery to morality.
Most freethinkers employ the simple yardsticks of reason and kindness.
This also embraces a respect for our planet, including the other animals, and feminist principles of equality. Moral dilemmas involve a conflict of values, requiring a careful use of reason to weigh the outcomes. Freethinkers try to base actions on their consequences to real, living human beings. Freethinkers know that meaning must originate in a mind. Since the universe is mindless and the cosmos does not care, you must care, if you wish to have purpose.