Fixing our attention now upon the real changes which characterize the data of our experience, let us inquire what conditions are necessary in order that an intrinsically possible object of thought become here and now an actual being. It matters not whether we select an example from the domain of organic nature, of inorganic nature, or of art—whether it be an oak, or an iceberg, or a statue. In order that there be here and now an actual oak-tree, it is necessary not only (1) that such an object be intrinsically possible, but (2) that there have been planted here an actual acorn, _i.e._ an actual being having in it subjectively and really the passive potentiality of developing into an actual oak-tree, and (3) that there be in the actual things around the acorn active powers or forces capable of so influencing the latent, passive potentiality of the acorn as gradually to evolve the oak-tree therefrom. So, too, for the (1) intrinsically possible iceberg, there are needed (2) water capable of becoming ice, and (3) natural powers or forces capable of forming it into ice and setting this adrift in the ocean. And for the (1) intrinsically possible statue there are needed (2) the block of marble or other material capable of becoming a statue, and (3) the sculptor having the power to mould this material into an actual statue. In order, therefore, that a thing which is not now actual, but only intrinsically or absolutely possible, become actual, there must actually exist some being or beings endowed with the _active power or potency_ of making this possible thing actual. The latter is then said to be _relatively, extrinsically_ possible—in relation to such being or beings. And obviously a thing may be possible relatively to the power of one being, and not possible relatively to lesser power of another being: the statue that is intrinsically possible in the block of marble, may be extrinsically possible relatively to the skilled sculptor, but not relatively to the unskilled person who is not a sculptor. Furthermore, relatively to the same agent or agents, the production of a given effect, the doing of a given thing, is said to be _physically_ possible if it can be brought about by such agents acting according to the ordinary course of nature; if, in other words they have the physical power to do it. Otherwise it is said to be physically impossible, even though metaphysically or intrinsically possible, _e.g._ it is physically impossible for a dead person to come to life again. A thing is said to be _morally_ possible, in reference to free and responsible agents, if they can do it without unreasonable inconvenience; otherwise it is considered as morally impossible, even though it be both physically and metaphysically possible: as often happens in regard to the fulfilment of one’s obligations.