Tabula rasa literally means "blank slate". It refers, however, to a state of mind that is, not merely naive, but untested and untried. And with reference to reality, altogether unfit for dealing with the world at large.
Showing our hand
"Give not that which is holy unto the dogs, neither cast ye your pearls before swine, lest they trample them under their feet, and turn again and rend you." (Matthew 7:6)
Did Jesus just call some people "swine"? Yes. He also said you had something that was holy. How many of us realize that the ways in which God has revealed Himself to us are holy? I think that's the least common denominator to which Jesus is referring in this verse. And unless we clearly mark off inside, that which is sacred (the aforementioned blessings of God) and that which is profane, we could be spilling priveleged information to those who, to put it politely, don't have our best interests at heart. And to put it not-so-politely (i.e. actually), swine.
"A fool uttereth all his mind: but a wise man keepeth it in till afterwards." (Proverbs 29:11)
That's the trouble with some people. They have no introspection. I don't mean to sound harsh and I am not seeking to belittle anyone at all. But when someone puts their foot in their mouth by speaking things out about their life that are no one's business but God's, my heart goes out to them. Call it gut-feeling, intuition, sixth sense (Richard Lederer, in his book More Anguished English says the "sense of humor" is the sixth one, funny.), ESP, whatever. There's only so much you can do with the person who has no qualms about sharing secrets in light of a world that is starving for some vestige, however small, of God's life--without actually going to God to get it themselves. And so, I don't know what's worse, being a "swine". Or being a "dog". Animal comparisons are a sketchy field. My favorite bird used to be the Bald Eagle (Haliaeetus leucocephalus) until I moved on and started liking the Raven (Corvus corax). Turns out both have strengths and weaknesses. While the eagle can soar sky-high and stare into the sun and descend to pull a fish from the water, it's also a scavenger. Much of its diet consists of things already dead. How's that for the untarnished image of the noble eagle? The raven, while it may be a scavenger and adept at trickery and mockery, is probably the most intelligent of birds and equipped with more intricate flight and vocal patterns. Too much information, I digress. Whoops.
There's another side to this. When someone shows an untempered and ungoverned mouth, for lack of a better term, and you see the folly in their conversation, or, the way they're living, don't just internally criticize them. I've been on both sides of the issue with this. Someone who unspools, or "uttereth all [their] mind" may well have their heart right with God. I don't know. And so if I'm going to listen to them open up to me about things of a sensitive nature, I'd best be lifting them up in prayer that they don't hurt themselves. It's funny how a "wolf in sheep's clothing" has the same connotation in this context, as a "swine" that, after hearing you spill your guts (or me, mine) would "turn again and rend you". Not much in the way of positivity for either the wolf, or the pig, in this case.
I suppose, then, that the state of tabula rasa is indeed a desirable one. To have a mind untouched by all the sin and darkness and depression loose in the world. And because of what Jesus did for us, it's now possible--encouraged and commanded, even--to attain. When Jesus takes our sin, He gives us that better thing--that "pearl". That which takes from the grit and grime at the depth of the sea and is transformed into a thing of exquisite beauty. Don't give it away.
In closing, Paul says this: "Brethren, be not children in understanding: howbeit in malice be ye children, but in understanding be men." Or women. (1 Corinthians 14:20) In other words, don't remain naive to the ways of the world. And don't hurt others who are naive in the ways of God.
"Behold, I send you forth as sheep in the midst of wolves: be ye therefore wise as serpents, and harmless as doves." (Matthew 10:16) Who knew the snake had any positive attributes?