For the motions of the bodily spirits are inseparable from, and according to, the state and action of the mind: when reason is in speculation of a trifle, they concur but weakly; when reason speculates intensely, their operation is increased. And sometimes the attention of the mind is so great, and has so engaged and called in all the animal spirits to its assistance, that the operations of our senses are suspended, and we neither see, nor feel, till the attention of the mind has let the spirits return to all the parts of the body. Now will any one say, that these intense thoughts are less the acts of the mind, because they have a greater concurrence of bodily spirits, than when it is acting with indifference, and so has a lesser quantity of bodily spirits? Yet this might as well be said, as to say, that the assent or dissent, in speculation, is the act of our reason; but liking or disliking, loving or hating, are not the acts of our reason, because they have a greater concurrence of bodily spirits. For, as the mind is in a different state when it desires good, or fears evil, from what it is when it only compares two triangles; so the motions of the bodily spirits, have only _such_ a difference, as is _correspondent_ to these two states of the mind. They act and join as much in comparing the triangles, as in the desire of good, or fear of evil. And the mind is just as much governed by the body, in its passions, as in its calmest contemplations. For as the gentle operation of the animal spirits is then correspondent to the state and action of the mind; so in all our passions, the strong and increased motion of the animal spirits, is equally correspondent thereto. So that reason is no more the agent, in our tempers and passions, than in our dry and sedate speculations. It may happen, that a man may have as great an eagerness in solving a mathematical problem, as another hath to obtain any great good, or avoid any great evil. But may it therefore be said, that it is not reason that solves the problem, because the bodily spirits are so active in it? To draw now some plain consequences from the foregoing account. _First_, If reason be the _universal agent_ in the natural man; if all the difference among _such_ men, is only such a difference as reason makes, then nothing can be more extravagant, than to affirm any thing concerning the degree of perfection, or imperfection of reason, as _common_ to man. It is as wild and romantic, as to pretend to state the measure of folly and wisdom, of fear and courage, of pride and humility, of good humour and ill-humour, _common_ to mankind: for as these states of the mind, are only so many different states of reason; so no uncertainty belongs to them, but what, in the _same degree_, belongs to _reason_.