The great Reformer warned of both dangers: extravagance and asceticism. Both ignore the fact that it is God who gives the material things of life. This is excerpted from Calvin’s Institutes, Book III, chapter 10.

1. Double Danger: Mistaken Strictness and Mistaken Laxity

By such elementary instruction, Scripture at the same time duly informs us what is the right use of earthly benefits—a matter not to be neglected in the ordering of our life. For if we are to live, we have also to use those helps necessary for living. And we also cannot avoid those things which seem to serve delight more than necessity. Therefore we must hold to a measure so as to use them with a clear conscience, whether for necessity or for delight. By his word the Lord lays down this measure when he teaches that the present life is for his people as a pilgrimage on which they are hastening toward the Heavenly Kingdom [Lev. 25:23; 1 Chron. 29:15; Ps. 39:13; 119:19; Heb. 11:8–10,13–16; 13:14; 1 Peter 2:11]. If we must simply pass through this world, there is no doubt we ought to use its good things in so far as they help rather than hinder our course. Thus Paul rightly persuades us to use this world as if not using it; and to buy goods with the same attitude as one sells them [1 Cor. 7:31.

But because this topic is a slippery one and slopes on both sides into error, let us try to plant our feet where we may safely stand. There were some otherwise good and holy men who when they saw intemperance and wantonness, when not severely restrained, ever raging with unbridled excess, desired to correct this dangerous evil. This one plan occurred to them: they allowed man to use physical goods in so far as necessity required. A godly counsel indeed, but they were far too severe. For they would fetter consciences more tightly than does the Word of the Lord—a very dangerous thing. Now, to them necessity means to abstain from all things that they could do without; thus, according to them, it would scarcely be permitted to add any food at all to plain bread and water. And others are even more severe. We are told of Crates of Theban, that he cast all his goods into the sea; for he thought that unless they were destroyed, they would destroy him.

But many today, while they seek an excuse for the intemperance of the flesh in its use of external things, and while they would meanwhile pave the road to licentious indulgence, take for granted what I do not at all concede to them: that this freedom is not to be restrained by any limitation but to be left to every man’s conscience to use as far as seems lawful to him. Certainly I admit that consciences neither ought to nor can be bound here to definite and precise legal formulas; but inasmuch as Scripture gives general rules for lawful use, we ought surely to limit our use in accordance with them.

2. The Main Principle

Let this be our principle: that the use of God’s gifts is not wrongly directed when it is referred to that end to which the Author himself created and destined them for us, since he created them for our good, not for our ruin. Accordingly, no one will hold to a straighter path than he who diligently looks to this end. Now if we ponder to what end God created food, we shall find that he meant not only to provide for necessity for also for delight and good cheer. Thus the purpose of clothing, apart from necessity, was comeliness and decency. In grasses, trees, and fruits, apart from their various uses, there is beauty of appearance and pleasantness of odor [cf. Gen. 2:9]. For if this were not true, the prophet would not have reckoned them among the benefits of God, “that wine gladdens the heart of man, that oil makes his face shine” [Ps. 104:15]….

3. a Look at the Giver of the Gift Prevents Narrow-Mindedness and Immoderation

Away, then, with that inhuman philosophy which, while conceding only a necessary use of creatures, not only malignantly deprives us of the lawful fruit of God’s beneficence but cannot be practiced unless it robs a man of all his senses and degrades him to a block.

But no less diligently, on the other hand, we must resist the lust of the flesh, which, unless it is kept in order, overflows without measure. And it has, as I have said, its own advocates, who, under the pretext of the freedom conceded, permit everything to it. First, one bridle is put upon it if it be determined that all things were created for us that we might recognize the Author and give thanks for his kindness toward us. Where is your thanksgiving if you so gorge yourself with banqueting or wine that you either become stupid or are rendered useless for the duties of piety and of your calling?…

4. Aspiration to Eternal Life Also Determines Aright Our Outward Conduct of Life

But there is no surer or more direct course than that which we receive from contempt of the present life and meditation upon heavenly immortality. For from this two rules follow: those who use this world should be so affected as if they did not use it; those who marry, as if they did not marry; those who buy, as if they did not buy, just as Paul enjoins [1 Cor. 7:29–31]. The other rule is that they should know how to bear poverty peaceably and patiently, as well as to bear abundance moderately….

Therefore, even though the freedom of believers in external matters is not to be restricted to a fixed formula, yet it is surely subject to this law: to indulge oneself as little as possible; but, on the contrary, with unflagging effort of mind to insist upon cutting off all show of superfluous wealth, not to mention licentiousness, and diligently to guard against turning helps into hindrances.

5. Frugality, Earthly Possessions Held in Trust

The second rule will be: they who have narrow and slender resources should know how to go without things patiently, lest they be troubled by an immoderate desire for them. If they keep this rule of moderation, they will make considerable progress in the Lord’s school. So, too, they who have not progressed, in some degree at least, in this respect have scarcely anything to prove them disciples of Christ. For besides the fact that most other vices accompany the desire for earthly things, he who bears poverty impatiently also when in prosperity commonly betrays the contrary disease. This is my point: he who is ashamed of mean clothing will boast of costly clothing; he who, not content with a slender meal, is troubled by the desire for a more elegant one, will also intemperately abuse those elegances if they fall to his lot. He who will bear reluctantly, and with a troubled mind, his deprivation and humble condition if he be advanced to honors will by no means abstain from arrogance. To this end, then, let all those for whom the pursuit of piety is not a pretense strive to learn, by the Apostle’s example, how to be filled and to hunger, to abound and to suffer want [Phil. 4:12].