If everything we do is completely determined by antecedent conditions, then we have no control over our actions. If we have no control over our actions, then nobody ever acts freely. Sometimes people act freely. If we have a control over our acts, then these acts are not completely determined by antecedent conditions. If not everything we do is completely determined by antecedent conditions, then some events are not caused.
Nobody ever does anything freely.
Sometimes we resist our passions. If sometimes we resist our passions, then sometimes we act freely. Sometimes we do what we choose to do. If sometimes we do what we choose to do, then sometimes we act freely. Sometimes we feel that we are acting freely, that we could have acted otherwise, and that nothing determine our acts.