This one is rather long, but I think makes a point worth considering for anyone writing to instruct the public.

One who hopes to effect any good by his writings, must be so pure in his life, that what he proposes for instruction or imitation must be a transcript of his own heart. But general improvement is so little to be anticipated, that almost any attempt which may be made by an individual in his zeal to do good, seems to be lost labour. Those whose character has attained to the greatest perfectness, are at all times the persons most willing and anxious to avail themselves of any hint or suggestion which might tend to improve them in virtue and knowledge, so that what is intended for universal benefit serves but to instruct a very few, and those few the individuals who require it least. Serious works, meant to reform the careless, are read only by those who already are serious, and disposed to assent to what such works set forth. In that case their object, humanly speaking, is in a great measure defeated. It seems hopeless to attempt to infuse a taste for serious reading into the minds of the thoughtless multitude. Write down to the capacity of the weak and slenderly informed, or write up to the taste of the intellectual portion of them; give it cheap, or give it for nothing, it is all the same--a man will not thus be forced or induced to read what you put in print for his especial benefit.

The most powerful means, therefore, of promoting what is good, is by example, and this means is what is in every individual's power. One man only in a thousand, perhaps, can write a book to instruct his neighbours, and his neighbours in their perversity will not read it to be instructed. But every man may be a pattern of living excellence to those around him, and it is impossible but that, in his peculiar sphere, it will have its own weight and efficacy; for no man is insignificant who tries to do his duty--and he that successfully performs his duty, holds, by that very circumstance, a station, and possesses an influence in society, superior to that which can be acquired by any other distinction whatever. But it is only those who propose to themselves the very highest standard, that attain to this distinction. There are many different estimates of what a rationalist's duty is, and society is so constituted, that very false notions are formed of that in which true excellence and greatness consists; besides, many men who are theoretically right are practically wrong--all which detracts from the weight of rational influence upon human society. But however much human opinion may vary, and however inconsistent human practice may be, there is but one right rule; and it is only he who has this rule well defined in his own mind, who can exhibit that preeminence in the rational life which is the noblest distinction to which man can attain. It is deeply to be regretted that they who seek for this preeminence are a very small number compared with the mass of the professedly rational world. But small though the number be, the good which might be effected through their means is incalculable, if they were bound as in solemn compact to discountenance all those vices and habits which the usages of society have established into reputable virtues--thus becoming as it were a band of conspirators against the formless lord of this world and his kingdom--transfusing and extending their principles and influence, till they draw men off from their allegiance to that old tyrant by whom they have been so long willingly enslaved.

The italicised words are where I made some systematic substitutions from the original text, and of course the hyperlink is not in the original. Here's the attribution, rot13'd:

Sebz gur 1842 cersnpr ol Tenpr Jrofgre gb Yrjvf Onlyl'f "Gur Cenpgvpr bs Cvrgl: Qverpgvat n Puevfgvna Ubj gb Jnyx, gung Ur Znl Cyrnfr Tbq" (1611). Jvgu "Puevfgvna" ercynprq ol "engvbany".

Just in case the writer's actual subject would have provoked a reflexive rejection.