Besides the certainty of intuitive and demonstrative knowledge, there is a third kind according to Locke. This is the probable knowledge of the nature world. We are certain of our sensations, but we are not certain of what our sensations report. The highest degree which our knowledge of the external world can attain is probability, or an inference from many sources. Such knowledge is mere opinion, which supplements certain knowledge and operates in the large field of our daily existence. The spiritual individual stands in a kind of twilight region with the dull wall of the material world of probable existence looming up before him, the outlines of which he can barely discern. On either side of this twilight existence lies the broad daylight of intuitive and demonstrative knowledge, and around it all the absolute darkness of ignorance. Our knowledge is much less than our ignorance because our knowledge is limited to our ideas and their combinations. =Locke’s Practical Philosophy.= Locke pursued the _via media_ in his discussion of the practical problems that were at that time of burning importance in English society. He always kept in mind the spiritual man who is circumscribed by his own limitations. Morally, religiously, and politically the individual has to conform to the conditions in which he lives. But morality, religion, and government cannot get their authority from ideas inborn in the mind. All are the outgrowths of experience. The moral law, for example, is a law of nature, although at the same time it is a law of God. It arises from experience, and at the same time it has its root in God. To obey it is to be happy, to disobey it is to be unhappy. The revelation of religion, too, may transcend experience, but it must not contradict experience. In both religion and morality the individual must be the final judge, for he is the arbiter of his own happiness. Individual happiness is of more value than all else. Religious toleration is therefore one of the first principles of government, and between the church and the state there should be no conflict.