I first came across Wesley's law in Dean Kelley's book, "Why Conservative Churches are Growing". Kelley's version of the law can be summarised as: "Taking up the religion has produced benefits which makes missionary zeal too costly to engage in". Essentially as people grow in grace they grow in respect and wealth making evangelism and enthusiasm a threat to their new status.
As Kelley puts it their zeal for mission is reduced. Kelley called the law "Wesley's law" because John Wesley's saw this principle in action in his Methodists and frequently warned against it.
I made use of this law in in my first published paper on the limited enthusiasm model in 1999 to justified why enthusiasts, those who are involved in recruitment and seeing others converted, do not stay enthusiastic indefinitely. Wesley clearly saw that revivals can burn out because of the limited period for which a Christian can remain seriously religious. So what exactly did Wesley say.
Kelley quoted the law from Max Weber (The Protestant Ethic and the Spirit of Capitalism, chapter 5). This is one of the classic sociology of religion texts and the one where the protestant work ethic was developed. Weber obtains his quote from Southey, Life of Wesley, chap. xxix:
"I fear, wherever riches have increased, the essence of religion has decreased in the same proportion. Therefore I do not see how it is possible, in the nature of things, for any revival of true religion to continue long. For religion must necessarily produce both industry and frugality, and these cannot but produce riches. But as riches increase, so will pride, anger, and love of the world in all its branches. How then is it possible that Methodism, that is, a religion of the heart, though it flourishes now as a green bay tree, should continue in this state? For the Methodists in every place grow diligent and frugal; consequently they increase in goods. Hence they proportionately increase in pride, in anger, in the desire of the flesh, the desire of the eyes, and the pride of life. So, although the form of religion remains, the spirit is swiftly vanishing away. Is there no way to prevent this-- this continual decay of pure religion? We ought not to prevent people from being diligent and frugal; we must exhort Christians to gain all they can, and to save all they can; that is, in effect, to grow rich." http://www.ne.jp/asahi/moriyuki/abukuma/weber/world/ethic/pro_eth_5a.html#par-asc
In the footnote Weber acknowledges another person for pointing out the reference.
95. Quoted in Southey, Life of Wesley, chap. xxix (second American edition, II, p. 308). For the reference, which I did not know, I am indebted to a letter from Professor Ashley (1913). Ernst Troeltsch, to whom I communicated it for the purpose, has already made use of it.
Weber was particular interested in the last part where Wesley justified it was a Christian duty to grow rich. However it is the earlier part about revival not continuing for long due to their belief producing riches and the riches causing them to drift from the purity of the faith - the decline of pure religion.
It is clear from the above quote that Southey did perform some editing on Wesley's original work. The standard edition of Wesley's work is by Jackson. This is normally available on CD but an article on Money by George Lyons quotes the 1872 Jackson edition which says:
When he was 83 (in 1786), Wesley wrote in frustration:
I am not afraid that the people called Methodists will ever cease to exist. But I am afraid, that they will exist only as a dead sect, having the form of religion without the power. And this undoubtedly will happen, unless they hold fast to the doctrine, spirit, and discipline with which they began.
I fear because I have seen that wherever riches have increased, with but few exceptions, the essence of religion, the mind that was in Christ, has decreased in the same proportion. Therefore, I do not see how it is possible, in the nature of things, for any revival of true religion to continue long. For religion must necessarily produce both industry and frugality; and these cannot but produce riches. But as riches increase, so will pride, anger, and love of the world in all its forms.
How, then, is it possible that Methodism as a religion of the heart should continue long? For the Methodists in every place grow diligent and frugal; consequently, they increase in goods. Hence they proportionately increase in pride, in anger, in the desire of the flesh, the desire of the eyes, and the pride of life. So, although the form of religion remains, the spirit is swiftly vanishing away.
Is there no way to prevent this continual decline of genuine religion? We ought not to forbid people to be diligent and frugal. We must exhort all Christians to gain all they can, and to save all they can. But to do so is, in effect, to urge them to grow rich! So how can we avoid letting our money send us to hell?
There is one way, and only one, under heaven. If those who “gain all they can,” and “save all they can,” will likewise “give all they can;” then, the more they gain, the more they will grow in grace.
Wesley’s Works, 13: 258, 260-261, sections 1, 10-12, “Thoughts upon Methodism.” All references are to the 1872 Jackson edition of Wesley’s Works, which has been frequently reprinted by various publishers. For my research, I depended on the Providence House 1995 edition on CD-ROM. Available at: http://wesley.nnu.edu/misc_sermons/money.htm#_edn14
It is interesting to note that the section that Max Weber used to support his protestant work ethic no longer says the same thing. Wesley did not exhort his people to gain all they can and save all they can to become rich. Indeed he wanted them to avoid this trap. The last paragraph shows how: "gain all you can, save all you can, so you can give all you can!" Instead Weber stops the quote short and then explains the last part in his own words, but he then loses some of Wesley's impact.
As for Kelley's usage the meaning has stayed the same; riches lead to a decline of religion, which Wesley makes clear is the mind of Christ. The letter by Wesley also says that if this happens Methodism would become a dead sect, a form of religion without the power. It is remarkable that Wesley was realistic enough to see this when Methodism was at its most alive and powerful. He saw that unless the decay of pure religion was checked the church would cease to be effective. This is precisely how Kelley was seeing the declining lenient churches in his book. However Wesley does not predict decline or extinction. Perhaps this is because of the cultural norm of church growing and its position with the state. In that sense the decline of lenient churches is due to the leniency and spiritual weakness that Wesley foresaw and the changing context of society becoming more secular in its relationship to church.
Online, Complete Works of John Wesley
Wesley's words are contained in a letter called "Thoughts Upon Methodism". It can be found complete and (I think) unedited in the complete works of Wesley online at http://www.godrules.net/library/wesley/274wesley_m2.htm. The words are in the section called Supplementary Letters and it is given here with the online formatting
XXIII. Thoughts upon Methodism.
1. I AM not afraid that the people called Methodists should ever cease to exist either in Europe or America. But I am afraid, lest they should only exist as a dead sect, having the form of religion without the power. And this undoubtedly will be the case, unless they hold fast both the doctrine, spirit, and discipline with which they first set out. 2. What was their fundamental doctrine? That the Bible is the whole and sole rule both of Christian faith and practice. Hence they learned, (1.)That religion is an inward principle; that it is no other than the mind that was in Christ; or, in other words, the renewal of the soul after the image of God, in righteousness and true holiness. (2.)That this can never be wrought in us, but by the power of the Holy Ghost. (3.)That we receive this, and every other blessing, merely for the sake of Christ: And, (4.)That whosoever hath the mind that was in Christ, the same is our brother, and sister, and mother. 3. In the year 1729 four young students in Oxford agreed to spend their evenings together. They were all zealous members of the Church of England, and had no peculiar opinions, but were distinguished only by their constant attendance on the church and sacrament. In 1735 they were increased to fifteen; when the chief of them embarked for America, intending to preach to the heathen Indians. Methodism then seemed to die away; but it revived again in the year 1738; especially after Mr. Wesley (not being allowed to preach in the churches) began to preach in the fields.
One and another then coming to inquire what they must do to be saved, he desired them to meet him all together; which they did, and increased continually in number. In November, a large building, the Foundery, being offered him, he began preaching therein, morning and evening; at five in the morning, and seven in the evening, that the people’s labor might not be hindered. 4. From the beginning the men and women sat apart, as they always did in the primitive church; and none were suffered to call any place their own, but the first comers sat down first. They had no pews; and all the benches for rich and poor were of the same construction. Mr. Wesley began the service with a short prayer; then sung a hymn and preached, (usually about half an hour,) then sang a few verses of another hymn, and concluded with prayer. His constant doctrine was, salvation by faith, preceded by repentance, and followed by holiness. 5. But when a large number of people was joined, the great difficulty was, to keep them together. For they were continually scattering hither and thither, and we knew no way to help it. But God provided for this also, when we thought not of it. A year or two after, Mr. Wesley met the chief of the society in Bristol, and inquired, “How shall we pay the debt upon the preaching-house?” Captain Foy stood up and said, “Let every one in the society give a penny a week, and it will easily be done.” “But many of them,” said one, “have not a penny to give.” “True,” said the Captain; “then put ten or twelve of them to me. Let each of these give what they can weekly, and I will supply what is wanting.” Many others made the same offer. So Mr. Wesley divided the societies among them; assigning a class of about twelve persons to each of these, who were termed Leaders. 6. Not long after, one of these informed Mr. Wesley that, calling on such a one in his house, he found his quarrelling with his wife. Another was found in drink. It immediately struck into Mr. Wesley’s mind, “This is the very thing we wanted. The Leaders are the persons who may not only receive the contributions, but also watch over the souls of their brethren.” The society in London, being informed of this, willingly followed the example of that; in Bristol; as did every society from that time, whether in Europe or America. By this means, it was easily found if any grew weary or faint, and help was speedily administered. And if any walked disorderly, they were quickly discovered, and either amended or dismissed. 7. For those who knew in whom they had believed, there was another help provided. Five or six, either married or single men, met together at such an hour as was convenient, according to the direction of St. James, “Confess your faults one to another, and pray one for another, and ye shall be healed.” And five or six of the married or single women met together for the same purpose. Innumerable blessings have attended this institution, especially in those who were going on to perfection. When any seemed to have attained this, they were allowed to meet with a select number, who appeared, so far as man could judge, to be partakers of the same “great salvation.” 8. From this short sketch of Methodism, (so called,) any man of understanding may easily discern, that it is only plain, scriptural religion, guarded by a few prudential regulations. The essence of it is holiness of heart and life; the circumstantials all point to this. And as long as they are joined together in the people called Methodists, no weapon formed against them shall prosper. But if even the circumstantial parts are despised, the essential will soon be lost. And if ever the essential parts should evaporate, what remains will be dung and dross. 9. It nearly concerns us to understand how the case stands with us at present. I fear, wherever riches have increased, (exceeding few are the exceptions,) the essence of religion, the mind that was in Christ, has decreased in the same proportion. Therefore do I not see how it is possible, in the nature of things, for any revival of true religion to continue long. For religion must necessarily produce both industry and frugality; and these cannot but produce riches. But as riches increase, so will pride, anger, and love of the world in all its branches. 10. How, then, is it possible that Methodism, that is, the religion of the heart, though it flourishes now as a green bay-tree, should continue in this state? For the Methodists in every place grow diligent and frugal; consequently, they increase in goods. Hence they proportionably increase in pride, in anger, in the desire of the flesh, the desire of the eyes, and the pride of life. So, although the form of religion remains, the spirit is swiftly vanishing away. 11. Is there no way to prevent this? this continual declension of pure religion? We ought not to forbid people to be diligent and frugal: We must exhort all Christians to gain all they can, and to save all they can; that is, in effect, to grow rich! What way, then, (I ask again,) can we take, that our money may not sin; us to the nethermost hell? There is one way, and there is no other under heaven. If those who “gain all they can,” and “save all they can,” will likewise “give all they can;” then, the more they gain, the more they will grow in grace, and the more treasure they will lay up in heaven. LONDON, August 4, 1786.
Clearly the other works miss a substantial amount of text relating to the origins of Methodism to demonstrate that its commitment to holiness is part of the downfall of the enthusiasm. In system dynamics this would be called an unintended consequence. The attraction of Methodism was its holiness. This gave substance to the enthusiasm of the believers thus helping them bring more people into the movement and hence its growth. However the unintended consequence was that holiness led to people who could be trusted, which in turn led to a better lifestyle which now made their desire to express that enthusiasm costly and thus the religion of the heart waned. Once that lack of enthusiasm led to them being less effective in attracting people the growth would be undermined, the classic fix that fails archetype. Wesley's cure, to break the cause of the decline of pure religion, was to give their wealth away.
It should also be noted in the above letter that it is written in the third person, so Wesley refers to himself as "Mr Wesley" The letter does not appear to have a specific recipient. It is one of a number entitled "Thoughts Upon ...".
Wesley and Riches
Wesley preached a number of sermons on the danger of riches and his line never varied. From his journal he clearly found preaching on money the hardest of all as it was the topic that was heard with the least enthusiasm!
To give a flavour of his views here is a quote from sermon 116: "Causes Of The Inefficacy Of Christianity", starting from the middle of paragraph16
The Methodists grow more and more self-indulgent, because they grow rich. Although many of them are still deplorably poor; ("tell it not in Gath; publish it not in the streets of Askelon!") yet many others, in the space of twenty, thirty, or forty years, are twenty, thirty, yea, a hundred times richer than they were when they first entered the society. And it is an observation which admits of few exceptions, that nine in ten of these decreased in grace, in the same proportion as they increased in wealth. Indeed, according to the natural tendency of riches, we cannot expect it to be otherwise.
17. But how astonishing a thing is this! How can we understand it? Does it not seem (and yet this cannot be) that Christianity, true scriptural Christianity, has a tendency, in process of time, to undermine and destroy itself? For wherever true Christianity spreads, it must cause diligence and frugality, which), in the natural course of things, must beget riches! and riches naturally beget pride, love of the world, and every temper that is destructive of Christianity. Now, if there be no way to prevent this, Christianity is inconsistent with itself, and, of consequence, cannot stand, cannot continue long among any people; since, wherever it generally prevails, it saps its own foundation.
18. But is there no way to prevent this? -- to continue Christianity among a people? Allowing that diligence and frugality must produce riches, is there no means to hinder riches from destroying the religion of those that possess them? I can see only one possible way; find out another who can. Do you gain all you can, and save all you can? Then you must, in the nature of things, grow rich. Then if you have any desire to escape the damnation of hell, give all you can; otherwise I can have no more hope of your salvation, than of that of Judas Iscariot.
The parts in bold highlight the main points of "Wesley's Law" as given in his letter of 1786. This law was not an isolated quote from Wesley but something at the heart of his message to churches that were going lukewarm.