The means for arriving at truth in the order of nature is an active search according to certain well-known methods. It farther involves the negative condition of perfect freedom to canvass, to controvert, or to refute, every received doctrine or opinion. There is no use in going after new facts, or in rising to new generalities, if we are not to be allowed to displace errors. This is now conceded, except at the points of contact of the natural and the supernatural. In spite of the wide separation of the two worlds--the world of fact and the world of imagination,--we cannot conceive the second except in terms of the first; and if the shaping of the supernatural acquires fixity and consecration, the natural facts made use of in the fabric acquire a corresponding fixity, even although the rendering is found to be inaccurate. The prevailing conception of a future life needs a view of the separate and independent subsistence of the mental powers of man, very difficult to reconcile with present knowledge. * * * * * The growth of intolerance is quite explicable, but the explanation is not necessarily a justification. Although every division of the human family must have passed through many social phases, and must therefore have experienced revolutionary shocks, yet the rule of man's existence has been a rigorous fixity of institutions, with a hatred of change. Innovations, when not the effect of conquest, would be made under the pressure of some great crisis, or some tremendous difficulty that could not otherwise be met. The idea of individuals being allowed, in quiet times, to propose alterations in government, in religion, in morals, or even in the common arts of life, was thought of only to be stamped out. There was a step in advance of the ancient and habitual order of things, when an innovating citizen was permitted to make his proposal to the assembled tribe, with a rope about his neck, to be drawn tight if he failed to convince his audience. This might make men think twice before advancing new views, but it was not an entire suppression of them. The first introduction of the great religions of the world would in each case afford an interesting study of the difficulties of change and of the modes of surmounting these difficulties. There must always have concurred at least two things,--general uneasiness or discontent from some cause or other; and the moral or intellectual ascendency of some one man, whose views, although original, were yet of a kind to be finally accepted by the people. These conditions are equally shown in political changes, and are historically illustrated in many notable instances. It is enough to cite the Greek legislation of Lycurgus and of Solon.