Hume lists 3 possibilities: from observing things cannot get it from seeing things in the world. Only see cause of conjunctions, do not see the cause of links form the world: know about causality from our experience of power over our own bodies. We do not experience the power, because its not true the mind has power over the body, e. g. wanting to grow hair instantly. It is a discovered fact, not too hard to imagine things. Mind is not at all good at controlling the sentiments. This must be where impression of necessary connection comes fromit is the customary transition from a to belief of b. Official solution - feeling of compulsion comes with the transition. With a comes the thought of b; cannot resist the thought of b source of idea with necessary connection. the sentiment that accompanies it, not the transition. The association of ideas from one thing we associate the other.