I. First, what are vain thoughts? (1) There are the vain, worldly thoughts, which we must hate. Thoughts which in themselves are perfectly harmless and innocent may become vain through being welcomed and entertained at the wrong season. The same thoughts may become sinful and vain through mere excess, through occupying our minds overmuch. The world must be very near us when the worldly thought is ever with us. Our treasure, our best treasure, must assuredly be there, else our heart and the thought of our heart would not be always there also. (2) But if a wise man will watch against these thoughts about this world, which are only sinful when indulged or allowed at a wrong time or in excess, how much more will he hate those that in their nature and essence are sinful, as, for example, impure thoughts, being such as more than any other sully and defile the mirror of the soul, and render it incapable of giving back the pure image of God. (3) The transition to other thoughts, to such as we more immediately ascribe to the devil, is easy. It will be enough to indicate proud thoughts in general as the third division of those we have to consider.
II. Consider the remedies for vain thoughts. Chase them wholly away we never shall, but let them find no entertainment from us. As often as they visit us, let them drive us to Him by whose holy inspiration alone we are able either to think those things which be good, or to refuse to think those things which be evil; let them drive us to Him in a real, though it may be a voiceless, prayer, in a brief meditation on the glories of heaven or on the pains of hell, or on Christ hanging upon His Cross and bearing there the penalty of our sins, or on Christ coming to judgment and bringing to light all hidden things of darkness, and this wicked thought of ours among the rest. In devices such as these we must find our help.
R. C. Trench, Sermons New and Old,p. 123 (see also Sermons Preached in Ireland,p. 201).
References: Psalms 119:113. J. Vaughan, Children's Sermons,1875, pp. 109, 120; H. F. Burder, Sermons,p. 13; New Manual of Sunday-school Addresses,p. 253.