Swedenborg typically links rationality and freedom together and discusses them as a pair. He describes them as two faculties, or abilities, which distinguish human beings from animals, and are different from what appear to be some similar abilities in animals. These faculties are given to people by the Lord, and He does his best to preserve them in us since they are the means by which we can develop a true loving relationship with Him.
Rationality is the ability of the intellect to understand what is true and good (and the opposite, what is false and evil), and therefore to see the relationship between what is spiritual and eternal and what is natural and temporal. Freedom is the ability of the will to freely think, will, and do what is true and good (or the opposite), and therefore to choose eternal life or a merely worldly life - the life of heaven or the life of hell.
Rationality is particularly important in developing our understanding of spiritual truth. It forms the bridge between natural concerns and spiritual understanding, and is important in our regeneration. We need to allow ourselves to be lead by God in order to see what is really true, and put it into practice.
(References: Divine Love and Wisdom 240, 264, 266, 425; Divine Providence 73-76, 77, 276; The Doctrine of Life for the New Jerusalem 15)
