Section 4: A Free and Steady Mind explained simply

IV. Our highest good may also be defined otherwise, that is to say, the same idea may be expressed in different language. Just as the same army may at one time be extended more widely, at another contracted into a smaller compass, and may either be curved towards the wings by a depression in the line of the centre, or drawn up in a straight line, while, in whatever figure it be arrayed, its strength and loyalty remain unchanged; so also our definition of the highest good may in some cases be expressed diffusely and at great length, while in others it is put into a short and concise form. Thus, it will come to the same thing, if I say “The highest good is a mind which despises the accidents of fortune, and takes pleasure in virtue”: or, “It is an unconquerable strength of mind, knowing the world well, gentle in its dealings, showing great courtesy and consideration for those with whom it is brought into contact.” Or we may choose to define it by calling that man happy who knows good and bad only in the form of good or bad minds: who worships honour, and is satisfied with his own virtue, who is neither puffed up by good fortune nor cast down by evil fortune, who knows no other good than that which he is able to bestow upon himself, whose real pleasure lies in despising pleasures. If you choose to pursue this digression further, you can put this same idea into many other forms, without impairing or weakening its meaning: for what prevents our saying that a happy life consists in a mind which is free, upright, undaunted, and steadfast, beyond the influence of fear or desire, which thinks nothing good except honour, and nothing bad except shame, and regards everything else as a mass of mean details which can neither add anything to nor take anything away from the happiness of life, but which come and go without either increasing or diminishing the highest good? A man of these principles, whether he will or no, must be accompanied by a continual cheerfulness, a high happiness, which comes indeed from on high because he delights in what he has, and desires no greater pleasures than those which his home affords. Is he not right in allowing these to turn the scale against petty, ridiculous, and shortlived movements of his wretched body? on the day on which he becomes proof against pleasure he also becomes proof against pain. See, on the other hand, how evil and guilty a slavery the man is forced to serve who is dominated in turn by pleasures and pains, those most untrustworthy and passionate of masters. We must, therefore, escape from them into freedom. This nothing will bestow upon us save contempt of Fortune: but if we attain to this, then there will dawn upon us those invaluable blessings, the repose of a mind that is at rest in a safe haven, its lofty imaginings, its great and steady delight at casting out errors and learning to know the truth, its courtesy, and its cheerfulness, in all of which we shall take delight, not regarding them as good things, but as proceeding from the proper good of man.