He who learns but does not think, is lost! He who thinks but does not learn is in great danger.

Taking in material without digesting it leaves you full of other people’s conclusions and unable to use any of them. Reasoning without taking anything in leaves you confident and unchecked, building elaborate structures on whatever happens to be lying around in your head. Both failures feel like intellectual activity from the inside, which is why they last so long.

Pair the two on purpose: after reading something substantial, close it and write what you now think in your own words. After reasoning your way to a strong opinion, go and find out what people who studied it actually say. Whichever half you enjoy less is probably the half you need.