Spinoza's Ethics: III.D2: Active Vs. Passive

Nos tum agere dico cum aliquid in nobis aut extra nos fit cujus adæquata sumus causa hoc est (per definitionem præcedentem) cum ex nostra natura aliquid in nobis aut extra nos sequitur quod per eandem solam potest clare et distincte intelligi. At contra nos pati dico cum in nobis aliquid fit vel ex nostra natura aliquid sequitur cujus nos non nisi partialis sumus causa.

Next I say that we are active when something in us or outside us happens of which we are the adequate cause, that is (by III.D1) when from our nature something in us or outside us follows which, through the same (nature) alone, is able to be understood clearly and distinctly. But in contrast I say that we are passive when in us something happens or from outside our nature something follows of which we are not the cause unless partially.  

Here Spinoza builds on the concept of adequate cause in the prior definition. The idea of being a sole cause is a high bar for adequacy. For example, it would seem that I am the cause of my breathing, but according to the rigor of Spinoza's definition, that does not seem true. I require oxygen for breathing and this is not something I generate myself. However, the part of the process of breathing which occurs after I have gotten oxygen may be an area in which I am the adequate cause. If this is true, then breathing is a complex process in which part of it is active (after getting oxygen) and the other part is passive (getting the oxygen).