The light of the body is the eye We must bear in mind, as I have already hinted, that what we find here are detached sentences, and not a continued discourse. The substance of the present statement is, that men go wrong through carelessness, because they do not keep their eye fixed, as they ought to do, on the proper object. For whence comes it, that they so shamefully wander, or dash themselves, or stumble, but because, having corrupted their judgment by choosing rather to follow their own lusts than the righteousness of God, they not only extinguish the light of reason, which ought to have regulated their life, but change it altogether into darkness. When Christ calls the eye the light of the body, [1] he employs a comparison which means, that neither the hands, nor the feet, nor the belly, serves to direct men in walking, but that the eye alone is a sufficient guide to the rest of the members. If the hands and feet are foolishly and improperly directed, the blame of the mistake ought to be charged on the eyes, which do not perform their duty. We must now apply this comparison to the mind. The affections may be regarded individually as its members: but as they are blind in themselves, they need direction. Now, God has given reason to guide them, and to act the part of a lantern in showing them the way. But what is the usual result? All the soundness of judgment which had been given to men is corrupted and perverted by themselves, so that not even one spark of light continues to dwell in them. A simple eye means an eye that has no speck, or diseased humor, or any other defect. An evil eye (poneron) [2] means a diseased eye. A luminous body means one that is enlightened, so as to have all its actions properly regulated. A dark body is one which is led into numerous mistakes by a confused movement. We see, then, as I have already said, that these words reprove the indolence of men, who neglect to open their eyes for the guidance of their affections. The inference which the Papists draw from this passage, that men possess as much reason and wisdom, as to be free to choose either good or evil, is mere trifling. For Christ does not here inform us what ability we possess, but how we ought to walk, by having our eye fixed on a certain object; and at the same time shows, that the whole course of human life is dark, because no man proposes for himself a proper object, but all permit themselves to pursue eagerly what is evil. I confess, indeed, that men naturally possess reason, to distinguish between vices and virtues; but I say that it is so corrupted by sin, that it fails at every step. Meanwhile, it does not follow, that men do not voluntarily bring darkness on themselves, as if they shut their eyes to avoid the light which was offered to them, because they are knowingly and willingly carried after their own lusts.

Footnotes

1 - "Appelant l'ceil le flambeau ou la lampe de tout le corps;" -- "calling the eye the torch or the lamp of the whole body."

2 - This Greek word has two meanings, which depend on accentuation. The proparoxytone poneros means laborious, troublesome: but the oxytone poneros means wicked Here, when applied to the eye, it cannot denote moral blame, but easily takes the transferred sense of faulty, defective. -- Ed

The light of the body - The sentiment stated in the preceding verses - the duty of fixing the affections on heavenly things - Jesus proceeds to illustrate by a reference to the "eye." When the eye is directed steadily toward an object, and is in health, or is single, everything is clear and plain. If it vibrates, flies to different objects, is fixed on no one singly, or is diseased, nothing is seen clearly. Everything is dim and confused. The man, therefore, is unsteady. The eye regulates the motion of the body. To have an object distinctly in view is necessary in order to correct and regulate action. Rope-dancers, that they may steady themselves, fix the eye on some object on the wall, and look steadily at that. If they should look down on the rope or the people, they might become dizzy and fall. A man crossing a stream on a log, if he will look across at some object steadily, will be in little danger. If he looks down on the dashing and rolling waters, he will become dizzy, and fall. So Jesus says, in order that the conduct may be right, it is important to fix the affections on heaven. Having the affections there - having the eye of faith single, steady, unwavering - all the conduct will be correspondent.
Single - Steady, directed to one object. Not confused, as persons' eyes are when they see double.
Thy body shall be full of light - Your conduct will be regular and steady. All that is needful to direct the body is that the eye be fixed right. No other light is required. So all that is needful to direct the soul and the conduct is, that the eye of faith be fixed on heaven; that the affections be there.
If, therefore, the light that is in thee - The word "light," here, signifies "the mind," or principles of the soul. If this is dark, how great is that darkness! The meaning of this passage may be thus expressed: The light of the body, the guide and director, is the eye. All know how calamitous it is when that light is irregular or extinguished, as when the eye is diseased or lost. So the light that is in us is the soul. If that soul is debased by attending exclusively to earthly objects - if it is diseased, and not fixed on heaven how much darker and more dreadful will it be than any darkness of the eye! Avarice darkens the mind, obscures the view, and brings in a dreadful and gloomy night over all the faculties.

The light of the body is the eye - That is, the eye is to the body what the sun is to the universe in the day time, or a lamp or candle to a house at night.
If - thine eye be single - Απλους, simple, uncompounded; i.e. so perfect in its structure as to see objects distinctly and clearly, and not confusedly, or in different places to what they are, as is often the case in certain disorders of the eye; one object appearing two or more - or else in a different situation, and of a different color to what it really is. This state of the eye is termed, Matthew 6:23, πονηρος evil, i.e. diseased or defective. An evil eye was a phrase in use, among the ancient Jews, to denote an envious, covetous man or disposition; a man who repined at his neighbor's prosperity, loved his own money, and would do nothing in the way of charity for God's sake. Our blessed Lord, however, extends and sublimes this meaning, and uses the sound eye as a metaphor to point out that simplicity of intention, and purity of affection with which men should pursue the supreme good. We cannot draw more than one straight line between two indivisible points. We aim at happiness: it is found only in one thing, the indivisible and eternal God. It the line of simple intention be drawn straight to him, and the soul walk by it, with purity of affection, the whole man shall be light in the Lord; the rays of that excellent glory shall irradiate the mind, and through the whole spirit shall the Divine nature be transfused. But if a person who enjoyed this heavenly treasure permit his simplicity of intention to deviate from heavenly to earthly good; and his purity of affection to be contaminated by worldly ambition, secular profits, and animal gratifications; then, the light which was in him becomes darkness, i.e. his spiritual discernment departs, and his union with God is destroyed: all is only a palpable obscure; and, like a man who has totally lost his sight, he walks without direction, certainty, or comfort. This state is most forcibly intimated in our Lord's exclamation, How great a darkness! Who can adequately describe the misery and wretchedness of that soul which has lost its union with the fountain of all good, and, in losing this, has lost the possibility of happiness till the simple eye be once more given, and the straight line once more drawn.

(7) The light of the body is the eye: if therefore thine (g) eye be single, thy whole body shall be full of light.
(7) Men maliciously and wickedly put out even the little light of nature that is in them.
(g) The judgment of the mind: that as the body is with the eyes, so our whole life may be ruled with right reason, that is to say, with the Spirit of God who gives light to us.

The light of the body is the eye,.... Or, the "candle of the body is the eye"; for the eye is that in the body, as a candle is in the house; by the light of it, the several members of the body perform their office; and what is said of the eye of the body, is transferred to the eye of the mind:
if therefore thine eye be single: that is, if thy mind be liberal, generous, and bountiful: for Christ is still upon the same subject of liberality, and against covetousness; and here speaks entirely in the language of the Jews, who could easily understand him; in whose writings we read of three sorts of eyes; a good eye, a middling one, and an evil one; so in the offerings of the first fruits (s),
, "a good eye" gave the fortieth, the house Shammai say, the thirtieth part; a middling one, the fiftieth; and an evil one, the sixtieth part.''
Upon which the commentators say (t), a "good eye" means one that is liberal, and an "evil eye" the contrary: hence you often read (u) of "trading, dedicating", and "giving with a good" or "an evil eye"; that is, either generously, liberally, or in a niggardly and grudging manner; which may help us to the sense of our Lord in these words; whose meaning is, that if a man is not covetous, but his mind is disposed to generosity and liberality; if this be the case, as if he should say,
thy whole body shall be full of light: all thy actions will be influenced by this noble principle; thy whole life will be illuminated, guided and governed by it; thy mind will be cheerful and pleasant, and thy estate and condition will be prosperous and successful.
(s) Misn. Trumot, c. 4. sect. 3. (t) Maimon. Bartenora & Ez. Chayim in ib. (u) T. Bab. Bava Bathra, fol. 37. 2. & 71. 1. & 72. 1.

The light--the lamp.
of the body is the eye: if therefore thine eye be single--simple, clear. As applied to the outward eye, this means general soundness; particularly, not looking two ways. Here, as also in classical Greek, it is used figuratively to denote the simplicity of the mind's eye, singleness of purpose, looking right at its object, as opposed to having two ends in view. (See Proverbs 4:25-27).
thy whole body shall be full of light--illuminated. As with the bodily vision, the man who looks with a good, sound eye, walks in light, seeing every object clear; so a simple and persistent purpose to serve and please God in everything will make the whole character consistent and bright.

The light of the body is the eye. This is not an abrupt transition, but bears on the same subject. If one's eye is diseased, all he sees is wrong. So the mind, or conscience, is the light of the soul. If these be darkened, all is darkness; if these see aright, all is light.

The eye is the lamp of the body - And what the eye is to the body, the intention is to the soul. We may observe with what exact propriety our Lord places purity of intention between worldly desires and worldly cares, either of which directly tend to destroy. If thine eye be single - Singly fixed on God and heaven, thy whole soul will be full of holiness and happiness. If thine eye be evil - Not single, aiming at any thing else.