Can we replace radically a thought?

Yes, of course it ccan eventually disappear, but not if we keep "checking" or "monitoring" its disappearance, as we resurrect the old thought every time we check to see whther we have forgotten. Success, in this case, must take place without acknowledgement of success, as success is defined as having forgotten. Of course, if we neglect anything long enough, it will eventually perish. Think of this both culturally and in terms of individuals. There are certainly things in the culture that became obsolete, and so faded outand were forgotten. things pertaining to being a caveman, or things pertaining to travelling by horse and horse-drawn carriages which everyone once knew, but have by now become obsolete and forgotten. Any child even a hundred years ago knew how to trim a wick on a kerosens lamp and had an instinct for adjusting the height of the flame, but now no-one remembers. And, on an individual basis, there are things you noticed about sucking a pacifier when you were a toddler, now long since vanished. Perhaps you can be REMINDED of the fact that you sucked a pacifier but you probably never even think of it on your own, unless you are REMINDED of that fact, and probably DECADES go by during which you never even for a second recall that fact;furthermore, even when you ARE reminded of sucking pacifiers, you probably cannot recall thingsa BOUT it that once were very important to you. When thoughts become obsolete, they DO fade away, unless we are constantly reminded of them. And, when our philospohies and knowledges expland, they overwhelm and engulf smaller modes of thought much like an ocean engulfing a pond.