A primary facet of a genuinely liberal society is that Truth, per se, is negotiable. In fact, negotiation is the primary tool for reaching consensus on what is true in any given context. Obviously, science–as a means for sharing objective truths–is a powerful tool for reaching agreement, but the fact of the matter is it can’t speak to our internal lives. The sense of self is not an object. Awareness is not an object. Science can’t speak to what constitutes a life well lived, except perhaps by figuring out who lives happily, and copying them. But this is what computers do.
The alternative to negotiated agreement is imposition. I distinguish four cultural orders. In Liberalism, as stated, truth is approximated in dialogue. In Sacrificial orders, it is inherited and imposed. Heretics are burnt or exiled. In Sybaritic Leftism, theoretically you negotiate, but the process is easily abused: since they believe that all people are fundamentally good, they have no means by which to block people who do not compromise. All you need to do to get your way is insist on it, and call anyone who objects hateful. This is the problem the Scandinavians, Dutch, and others are having with Islamists. Nothing in their make-up disposes them to fight for principles.
In Cultural Sadeism, of course, there is no truth. Your relative truth will always be what you are told, but it is subject to change. The only objective truth is the relation you have with the State, that of object being acted upon.