Again, nobody knows by what means or by what method the mind moves the body, nor how many degrees of motion it can communicate to the body, nor with what speed it can move the body. So that it follows that when men say that this or that action of the body springs from the mind which has commanded over the body, they do not know what they say, and they do nothing but confess with pretentious words that they know nothing about the cause of the action, and see nothing in it to wonder at. But they will say, that whether they know or do not know by what means the mind moves the body, it is nevertheless in their experience that if the mind were not fit for thinking the body would be inert. They say, again, it is in their experience that the mind alone has power both to speak and be silent, and to do many other things which they therefore think to be dependent on a decree of the mind. But with regard to the first assertion, I ask them if experience does not also teach that if the body be sluggish the mind at the same time is not fit for thinking? When the body is asleep, the mind slumbers with it, and has not the power to think, as it has when the body is awake. Again, I believe that all have discovered that the mind is not always equally fitted for thinking about the same subject, but in proportion to the fitness of the body for this or that image to be excited in it will the mind be better fitted to contemplate this or that object. But my opponents will say, that from the laws of Nature alone, in so far as it is considered to be corporeal merely, it cannot be that the causes of architecture, painting, and things of this sort, which are the results of human art alone, could be deduced, and that the human body, unless it were determined and guided by the mind, would not be able to build a temple. I have already shown, however, that they do not know what the body can do, nor what can be deduced from the consideration of its nature alone, and that they find that many things are done merely by the laws of Nature which they would never have believed to be possible without the direction of the mind, as, for example, those things which sleep-walkers do in their sleep, and at which they themselves are astonished when they wake. I adduce also here the structure itself of the human body, which so greatly surpasses in workmanship all those things which are constructed by human art, not to mention what I have already proved, that an infinitude of things follows from Nature under whatever attribute it may be considered.