So far, I have discussed matter and things and the various ways that they exist and can be understood. However, the entire discussion was completed without detailed consideration of change. I have already proven that change is real and that change of substance requires that matter exist. So now we can consider the nature of change while considering what we have already learned about matter and things. All change has a goal and all change has two parts: a passive part and an active part.
The first part is the most important. Without understanding that all change has a goal, we cannot properly understand any particular changes at all. So when we pick up a apple, hold it in the air and then release it, it falls. The goal of the change of letting it go is falling. We know this because this is true of everything that is the same substance as the apple. So all apples fall when released above the ground. This is a regularity or pattern in nature. We know it is a pattern because it happened all or most of the time. If we supposed that the change had no goal, then there would be no pattern. Sometimes the apple might fall, and sometimes it might turn into a pig, freeze solid or fly upwards. Our experience of things in the world says that there are patterns of change. Therefore, change has goals.
All change has two parts: an active part and a passive part. The active part is what is causing the change. The passive part is the thing that is caused to exist by the active part. We call the passive part a potential. We call the active part a power. We know that nothing can be both a potential and a power in the same way and at the same time. If something were both a power and a potential, then it would both exist and not exist. A potential does not exist. If the power acts on it, then it comes into existence and is no longer potential. The power already exists. In order to cause something to happen, the thing doing the causing must exist. Therefore, nothing can be both a potential and a power at the same time and in the same way.
Finally, I claimed that all change has a goal. I only proved that most change has a goal most of the time. My proof for the absolute statement follows. If there were a change that did not have a goal, then there would be a change that had a power but no potential. A power is what does the causing. A potential does not exist, but is what would exist if the power acts. This means that the power points at a single thing if it has a single potential. In order for the power to point at no goal, it would have to point at no particular potential. To point at no particular potential is the same as pointing at no potential at all. If a power points at no potential, then there cannot be any change. There is only change if something begins to exist that did not exist before. Therefore, assuming that some changes do not have goals leads to a contradiction. Therefore, all changes have goals.
The next issue in our discussion of substance is a distinction between causes. All causes are not the same – as any good scientist knows.