A raw unconscious drive is at the heart of all sentient creatures. Schopenhauer called it the will-to-life, where as Spinoza used a more ancient term – the conatus. For both these philosophers this drive was at the root of existence itself, although they had different takes on it. For Schopenhauer it was wholly lamentable, being the cause of great suffering. For Spinoza, it was simply something to understand and through that understanding we could make life pleasurable and reduce the suffering that is inherent in its nature. Billions of creatures all striving to exist inevitably creates suffering, not least because they have to eat each other to survive.
The conatus is best understood as the inbuilt dynamic to persist in existence. In proposition seven, part three of The Ethics Spinoza says:
The conatus with which each thing endeavors to persist in its own being is nothing but the actual essence of the thing itself.
We, like everything else endeavor to persist in our being. This raw drive is unconscious and we experience pleasure as long as it is being satisfied. However since we encounter many other individuals with the same drive it is not uncommon for our conatus to be thwarted. At this point we become conscious of desires. Spinoza defines this phenomena right at the start of his Definitions of the Emotions in The Ethics:
Desire is the very essence of man insofar as his essence is conceived as determined to any action from any given affection of itself.
In other words, when we are affected by other things our desires are ignited. Maybe it is sexual desire, desire for food, for money – or whatever.
Spinoza goes on to claim that the conatus is the power of God or Nature itself. In proposition four in part four of The Ethics he says:
The power whereby each single thing, and consequently man, preserves its own being is the very power of God, or Nature …
The conatus is problematical for all creatures – eat or be eaten, dominate or be dominated, kill or be killed. Spinoza asserts that with each desire is an associated ambition, which is also problematical. In Definition of The Emotions in part three of The Ethics he states:
Ambition is the desire whereby all emotions are encouraged and strengthened; and thus this emotion can scarcely be overcome. For as long as a man is subject to any desire, he is necessarily subject to this one.
The solution to all of this, insofar as there is a solution, is understanding.