by nature
He was passive by nature.
He is like that by nature.
Ella tiene un buen corazón por naturaleza.
She has a good heart by nature.
I am an optimist by nature.
Él es por naturaleza una persona generosa.
He is by nature a generous person.
El hombre es un animal político por naturaleza.
Man is a political animal by nature.
Ella es una mujer de buen corazón por naturaleza.
She is a kind-hearted woman by nature.
Todos los hombres se odian por naturaleza.
All men hate each other by nature.
Ella es curiosa por naturaleza.
She is naturally curious.