Some men look at constitutions with sanctimonious reverence, and deem them like the arc of the covenant, too sacred to be touched. They ascribe to the men of the preceding age a wisdom more than human, and suppose what they did to be beyond amendment. I knew that age well; I belonged to it, and labored with it. It deserved well of its country. It was very like the present, but without the experience of the present; and forty years of experience in government is worth a century of book-reading; and this they would say themselves, were they to rise from the dead. I am certainly not an advocate for frequent and untried changes in laws and constitutions. I think moderate imperfections had better be borne with; because, when once known, we accommodate ourselves to them, and find practical means of correcting their ill effects. But I know also, that laws and institutions must go hand in hand with the progress of the human mind. As that becomes more developed, more enlightened, as new discoveries are made, new truths disclosed, and manners and opinions change with the change of circumstances, institutions must advance also, and keep pace with the times. Thanks for posting this letter. I like this quote. I get a lot of grief from certain posters for "trashing" the Constitution, so allow me to "appeal to authority" and second TJ's thoughts here, that constitutions are not infallible, and that experience ought to translate into advances and corrections of flaws.
...that laws and institutions must go hand in hand with the progress of the human mind. As that becomes more developed, more enlightened, as new discoveries are made, new truths disclosed, and manners and opinions change with the change of circumstances, institutions must advance also, and keep pace with the times. Be careful of this section. This passage is used by socialists to advance their cause, as it is so open to definition that it can accomodate any argument. The entire letter explains the limits of this passage.
I believe that Jefferson was creating room for the abolition of slavery.
The fact of the matter is that the human mind is not subject to progress. It is set. We now have a near-perfect method of distributing knowledge and few people take advantage of it; they will chop and dice the knowledge that is available to them so they may construct a salad of their own political views, while ignoring the importance of liberty.
Moreover, in this letter Jefferson was, for the most part, speaking of a State government -- not the federal. Within the letter Jefferson states the role of the federal and state governments. It deserves to be noted.