Not, therefore, to raise expectation, but to repress it, I here lay before your Lordship the plan of my undertaking, that more may not be demanded than I intend; and that, before it is too far advanced to be thrown into a new method, I may be advertised of its defects or superfluities. Such informations I may justly hope, from the emulation with which those, who desire the praise of elegance or discernment, must contend in the promotion of a design that you, my Lord, have not thought unworthy to share your attention with treaties and with wars.

In the first attempt to methodise my ideas I found a difficulty, which extended itself to the whole work. It was not easy to determine by what rule of distinction the words of this dictionary were to be chosen. The chief intent of it is to preserve the purity, and ascertain the meaning of our English idiom; and this seems to require nothing more than that our language be considered, so far as it is our own; that the words and phrases used in the general intercourse of life, or found in the works of those whom we commonly style polite writers, be selected, without including the terms of particular professions; since, with the arts to which they relate, they are generally derived from other nations, and are very often the same in all the languages of this part of the world. This is, perhaps, the exact and pure idea of a grammatical dictionary; but in lexicography, as in other arts, naked science is too delicate for the purposes of life. The value of a work must be estimated by its use; it is not enough that a dictionary delights the critick, unless, at the same time, it instructs the learner; as it is to little purpose that an engine amuses the philosopher by the subtilty of its mechanism, if it requires so much knowledge in its application as to be of no advantage to the common workman.

The Works of Samuel Johnson in Nine Volumes — Part 3

The title which I prefix to my work has long conveyed a very miscellaneous idea, and they that take a dictionary into their hands, have been accustomed to expect from it a solution of almost every difficulty. If foreign words, therefore, were rejected, it could be little regarded, except by criticks, or those who aspire to criticism; and however it might enlighten those that write, would be all darkness to them that only read. The unlearned much oftener consult their dictionaries for the meaning of words, than for their structures or formations; and the words that most want explanation are generally terms of art; which, therefore, experience has taught my predecessors to spread with a kind of pompous luxuriance over their productions.

The Works of Samuel Johnson in Nine Volumes — Part 3