Spinoza'a Ethics: I.D7: Free

Here Spinoza defines "free" in a way I would not have intuitively understood it. My sense of free is skewed by a notion of will, whereas Spinoza is setting up free as a result of internal powers of "its own nature" dominating. This free or libera which is a result of its own powers, or its own nature, contrasts with necessary or necessaria which is a result of external powers dominating. One core issue then seems to be defining "its own nature" or suae naturae. Free and necessary are a function of that definition.

Ea res libera dicitur quae ex sola suae naturae necessitate existit et a se sola ad agendum determinatur. Necessaria autem vel potius coacta quae ab alio determinatur ad existendum et operandum certa ac determinata ratione.

Translated as,

That thing is called free which exists from only the necessity of its own nature and is determined to act by itself alone. Moreover a thing is called necessary or rather compelled which is determined by something other [than its own nature] to exist and to operate in a certain and determinate manner.