If the foundation of building a house is not firm, it will inevitably be built too high, and it will fall down. Buildings with weak foundations are like saplings in the wind. No matter whether it is a petite swallow or a thin sparrow, there is no way to nest, hatch birds, shelter from the wind and rain and spend the winter on it. This image tells people the importance of foundation.
Building a house is like this, so is studying. Without extensive basic knowledge, it is difficult to study in depth in the later stage and go further in one field.