half knowledge...

at some point of time someone older than you would've told you that 'learning is a continuous process' 'half knowledge is dangerous' and 'ignorance is bliss'. If learning is a continuous process, then regardless of the knowledge you've already accumulated, there's still more to gather. That makes complete knowledge infinity.
if complete knowledge is infinity then half knowledge too cannot be quantised. That means that at any point of time, you have less than half knowledge. so there is no way of telling when you can stop learning.
but, if ignorance is bliss, knowledge is misery. As long as you're miserable, you have complete knowledge. as long as you're miserable there's no need to learn anything more.
hence we have proved that the first statement is false - learning cannot be a continuous process and knowledge cannot be infinity...

...now that we've established quantization of knowledge let's see it's application. you'd have noticed that knowledge is measured by the depth rather than length, breadth, height or weight. we know that as one goes deeper and deeper into the earth's crust temperature rises to a high at the core and starts to drop as one moves towards the other side.
ergo, half knowledge is dangerous as it can kill you and complete knowledge can take you places as you'll reach the other side. but best of all, ignorance is bliss as it lets you be where you were in the first place.