Apparently the Corinthians themselves had argued that morality was quite independent of a belief in immortality. For Paul goes on: "Be not deceived:" you cannot, however much you may think so, you _cannot_ hear such theories without having your moral convictions undermined and your tone lowered. This he conveys to them in a common quotation from a heathen poet--"Evil communications corrupt good manners;" that is to say, false opinions have a natural tendency to produce unsatisfactory and immoral conduct. To keep company with those whose conversation is frivolous or cynical, or charged with dangerous or false views of things, has a natural tendency to lead us to a style of conduct we should not otherwise have fallen into. Men do not always recognise this; they need the warning, "Be not deceived." The beginnings of conduct are so hidden from our observation, our lives are formed by influences so imperceptible, what we hear sinks so insidiously into the mind and mingles so insensibly with our motives, that we can never say _what_ we have heard without moral contamination. No doubt it is possible to hold the most erroneous opinions and yet to keep the life pure; but they are strong and guileless spirits who can preserve a high moral tone while they have lost faith in those truths which mainly nourish the moral nature of the mass of men. And many have found to their surprise and grief that opinions which they fancied they might very well hold and yet live a high and holy life, have somehow sapped their moral defences against temptation and paved the way for shameful falls. We cannot always prevent doubts, even about the most fundamental truths, from entering our minds, but we can always refuse to welcome such doubts, or to be proud of them; we can always be resolved to treat sacred things in a reverent and not in a flippant spirit, and we can always aim at least at an honest and eager seeking for the truth.