That guarding is plainly imposed as necessary, by the very constitution of our manhood. Our nature is evidently not a republic, but a monarchy. It is full of blind impulses, and hungry desires, which take no heed of any law but their own satisfaction. If the reins are thrown on the necks of these untamed horses, they will drag the man to destruction. They are only safe when they are curbed and bitted, and held well in. Then there are tastes and inclinations which need guidance and are plainly meant to be subordinate. The will is to govern all the lower self, and conscience is to govern the will. Unmistakably there are parts of every man's nature which are meant to serve, and parts which are appointed to rule, and to let the servants usurp the place of the rulers is to bring about as wild a confusion within as the Ecclesiast lamented that he had seen in the anarchic times when he wrote--princes walking and beggars on horseback. As George Herbert has it--
'Give not thy humours way; God gave them to thee under lock and key.'
Then, further, that guarding is plainly imperative, because there is an outer world which appeals to our needs and desires, irrespective altogether of right and wrong and of the moral consequences of gratifying these. Put a loaf before a starving man and his impulse will be to clutch and devour it, without regard to whether it is his or no. Show any of our animal propensities its appropriate food, and it asks no questions as to right or wrong, but is stirred to grasp its natural food. And even the higher and nobler parts of our nature are but too apt to seek their gratification without having the license of conscience for doing so, and sometimes in defiance of its plain prohibitions. It is never safe to trust the guidance of life to tastes, inclinations, or to anything but clear reason, set in motion by calm will, and acting under the approbation of 'the Lord Chief Justice, Conscience.'
But again, seeing that the world has more evil than good in it, the keeping of the heart will always consist rather in repelling solicitations to yielding to evil. In short, the power and the habit of sternly saying 'No' to the whole crowd of tempters is always the main secret of a noble life. 'He that hath no rule over his own spirit is like a city broken down and without walls.'
II. There is no effectual guarding unless God guards.
The counsel in Proverbs is not mere toothless moral commonplace, but is associated, in the preceding chapter, with fatherly advice to 'let thine heart keep my commandments' and to 'trust in the Lord with all thine heart.' The heart that so trusts will be safely guarded, and only such a heart will be. The inherent weakness of all attempts at self-keeping is that keeper and kept being one and the same personality, the more we need to be kept the less able we are to effect it. If in the very garrison are traitors, how shall the fortress be defended? If, then, we are to exercise an effectual guard over our characters and control over our natures, we must have an outward standard of right and wrong which shall not be deflected by variations in our temperature. We need a fixed light to steer towards, which is stable on the stable shore, and is not tossing up and down on our decks. We shall cleanse our way only when we 'take heed thereto, according to Thy word.' For even God's viceroy within, the sovereign conscience, can be warped, perverted, silenced, and is not immune from the spreading infection of evil. When it turns to God, as a mirror to the sun, it is irradiated and flashes bright illumination into dark corners, but its power depends on its being thus lit by radiations from the very Light of Life. And if we are ever to have a coercive power over the rebellious powers within, we must have God's power breathed into us, giving grip and energy to all the good within, quickening every lofty desire, satisfying every aspiration that feels after Him, cowing all our evil and being the very self of ourselves.