Naive and sentimental names Friedrich Schiller's distinction between two broad kinds of poets. Naive poets present the world directly and seem in harmony with nature, while sentimental poets write with more self-consciousness, reflection, and longing, often thinking about the loss of that natural ease. The terms describe a poet's attitude and method, not whether the poetry is simple or emotional.
Example
A naive poem might say:
The rain fell on the wheat
and the field drank it.
A sentimental poem might add:
I watch the same rain,
and feel how far I am
from the field it feeds.