This habit--it cannot be too often insisted on aids not only the acquisition of knowledge, but also its _retention_. Around these first principles, as around a standard, the thoughts naturally associate. Touch but a remote chord of any question, and it will vibrate to the central principle to which it has once been well attached. Every relative impression owns a kindred connection, and the moment one is attacked, it, like a faithful sentinel, arouses a whole troop, which, marshalled and disciplined, bear down and challenge the enemy.'* * Beauties and Uses of Euclid, pp. 47-9. What Rogers has so exquisitely sung of the associations of childhood, is true of the associations of science. Childhood's loved group revisit! every scene,-- The tangled wood-walk and the tufted green. The school's lone porch, with reverend mosses grey, Just tells the pensive pilgrim where it lay. Mute is the bell which rang at peep of dawn, Quick'ning my truant steps across the lawn: Unheard the shout that rent the noontide air, When the slow dial gave a pause to care. Up springs at every step, to claim a tear, Some little friendship formed and cherished here? And not the lightest leaf but trembling teems With golden visions and romantic dreams. CHAPTER VII. PROPOSITIONS All truth and all error lie in Propositions.--J. S. Mill. In accordance with that experience which directs to the profoundest books for the simplest statements, we turn to Mill's Logic for the philosophy of propositions. The answer to every question which it is possible to frame is contained in a proposition or assertion. Whatever can be an object of belief or even of disbelief, must, when put into words, assume the form of a proposition * * What we call a truth is simply a true proposition; and errors are false propositions. To know the import of all possible propositions would be to know all questions which can be raised, all matters which are susceptible of being either believed or disbelieved. * * Since then the objects of all belief and all inquiry express themselves in propositions, a sufficient scrutiny of propositions and of their varieties will apprise us what questions mankind have asked themselves, and what it the nature of the answers to those questions they have actually thought they had grounds to believe. 'Now the first glance at a proposition shows that it is formed by putting together two names. A proposition, according to the common simple definition, which is sufficient for our purpose, is, _discourse in which something is affirmed or denied of something_. Thus, in the proposition, gold is yellow, the quality _yellow_ is affirmed of the substance _gold_. In the proposition, Franklin was not born in England, the fact expressed by the words _born in England_ is denied of the man Franklin.