"What has been said of natural and moral necessity, may serve to explain what is intended by natural and moral _inability_. We are said to be _naturally_ unable to do a thing, when we cannot do it if we will, because what is most commonly called _nature_ does not allow of it, or because of some impeding defect or obstacle that is extrinsic to the will; either in the faculty of the understanding, constitution of body, or external objects." (p. 35.) We may make a voluntary endeavour to know something, and may find ourselves _unable_, through a defect of the understanding. We may make a voluntary effort _to do_ something by the instrumentality of our hand, and may find ourselves unable through a defect of the bodily constitution; or external objects may be regarded as presenting such a counter force as to overcome the force we exert. This is natural inability; this is all we mean by it. It must be remarked too, that this is _inability_ not _metaphysically_ or _philosophically_ considered, and therefore not _absolute_ inability; but only inability in the common and vulgar acceptation of the term--a relative inability, relative to volition or choice--an inability to do, although we will to do. What is moral inability? "Moral inability consists not in any of these things; but either in the want of inclination, or the strength of a contrary inclination, or the want of sufficient motives in view, to induce and excite the act of will, or the strength of apparent motives to the contrary. Or both these may be resolved into one; and it may be said, in one word, that moral inability consists in the opposition or want of inclination. For when a person is unable to will or choose such a thing, through a defect of motives, or prevalence of contrary motives, it is the same thing as his being unable through the want of an inclination, or the prevalence of a contrary inclination, in such circumstances and under the influence of such views." (bid.)