David Hume forms his theory of perceptions, which involves two major components: ideas and impressions. He uses this to form the very basis of his empiricist rule, which states that where there is an absence of an impression, the idea is meaningless. Hume also spoke of the workings of the human mind, which involves three laws of association of ideas: resemblance, contiguity, and cause and effect, with causality being the most powerful of them all. Hume claims that cause and effect plays a dominant role in all our thinking about factual matters. But from what impression does our idea of causality stem from? Our idea of causality arises from our impressions of three kinds of relations between objects: first, the relation of contiguity or contact, and second, temporal priority. These two, when taken together, Hume calls conjunction. The third kind of relationship that must also be present in our idea of cause and effect, is necessary connection. By necessary connection, Hume means the relation between cause and effect wherein the cause necessarily produces the effect. But from what impression do we derive the idea of necessary connection between cause and effect?