John Locke (1632-1704), philosopher, physician, friend of sydenham, and secretary to the Earl of shaftesbury, offered this advice about curiosity in children in a letter he wrote to Edward Clarke on September 1, 1685.
Curiosity in children is but an appetite after knowledge, and therefore ought to be encouraged in them, not only as a good sign, but as the great instrument nature has provided, to remove that ignorance they brought into the world with them, and which without this busy inquisitiveness would make them dull and useless creatures. The ways to encourage and keep it active and vigorous are, I suppose, the following:
First, not to check or discountenance any inquiries he may make, or suffer them to be laughed at; but to answer all his questions and explain matters he desires to know, so as to make them as much intelligible to him, as suits the capacity of his age and knowledge. But confound not this understanding with explications or notions that are above it, or with the variety or number of things that are not to his present purpose. Mark what it is he aims at in the question, and when you have informed and satisfied him in that, you shall see how his thoughts will proceed on to other things, and how by fit answers to his enquiries he may be led on farther than perhaps you could imagine.
For knowledge to the understanding is as acceptable as light to the eyes; and children are pleased and delighted with it exceedingly, especially if they see that their enquiries are regarded, and that their desire of knowing is couraged and commended.