|No, Ed, there is no contradiction.|
I wrote that "all 'forms, motions, combinations and dissolutions of elements within the universe' have causes and other determinants of their existence." Although inertial motions require no efficient causes to exist, they require material causes.
Thanks for the careful reading and notice.
The following background may be informative for some readers here. This is from my 1991 Objectivity essay "Induction on Identity" (V1N3).
"When one comes to formulate ideas about inanimate motion more generally, things become much less obvious, and customary experience can put one in the wrong frame of mind. It was very difficult for man to get straight which motions needed to be explained, which motions have causes in the primary sense. Today, students of physics learn the answer when they are taught the law of inertia, the law that a body will continue at constant speed and in a straight line (or will remain at rest) unless acted on by a force. At a more advanced level, students learn that and how the inertia principle has been recast in more general forms . . . .
"It is only the elementary form of the law of inertia that concerns us here. Aristotle and his followers held to principles contrary the inertia principle: Terrestrial bodies, when moving, naturally tend to move towards certain places of repose. The heavenly spheres, upon which ride the heavenly bodies, naturally and always move in circular ways. . . . Aristotle's camp took free fall of earthly bodies as natural and as standing in no need of special explanation; no external force is being applied to keep such bodies falling to the earth. Any other motion of an earthly body, any motion that is not free fall, needs special external explanation. Moreover, any motion at all requires some explanation. 'Everything that is in motion must be moved by something. For if it has not the source of its motion in itself, it is evident that it is moved by something else which moves it' (Ph. 7.1.241b34-36).
"What could be more sensible? In our life experiences here on the surface of the earth, we have countless confirmations of Aristotle's thesis every day. To get an object moving requires effort, to keep it moving requires effort, and the object will sooner or later return to rest. The strings of the harp will return to silence. For Galileo and his followers to propose that motion, provided it be uniform, required no explanation, no efficient cause, but that nonuniform motion, including coming to rest, did, they had to put on new thinking caps. . . . These men could not leave the answer to habitual experience (nor to tradition). Formulating physical principles simply according to the most usual observations would not have led men to the law of inertia. Until this law and its conceptual vantage were discovered, the scientific revolution could not happen.
"In common sense and in most scientific reasoning, we make the tried and true presumption that occurrences have causes. Hume discussed this principle in the venerated form "whatever begins to exist, must have a cause of existence." He contended that this principle is not a necessary truth. He may have even doubted the truth of the principle (T 78-82). We should distinguish two interpretations of the principle. In one we take cause as material cause, and in the other, we take cause as efficient cause. As to material cause, the principle seems to have held up perfectly in the two and a half centuries of science since Hume. It holds for all elementary particles; every particle gets made from some others. As to efficient cause, the principle holds always for cause in the broad mode; each type of elementary particle has its distinctive ways of coming about. . . . Again as to efficient cause, the principle evidently does not hold in the narrow mode for elementary particles. There is no narrow cause of the decay products. Remember, too, the proverb of particle physicists: 'Seek not reasons for decay, but seek barriers to decay'." (28-30)
Turning back a few pages, my distinction between the narrow and the broad modes:
"Hume's commonsense principle that same causes yield same effects was also endorsed by Aristotle: 'It is a law of nature that the same cause, provided it remain in the same condition, always produces the same effect' (GC 2.10.336a27-28). Ockham endorsed the principle in a form close to Hume's: 'Causes of the same kinds are effective of effects of the same kinds'. Ockham took this principle to be necessary and self-evident. As the principle is formulated by Ockham or Hume, it is subject to two interpretations. One, a broad one, I shall endorse in a moment. The other---and this is what both Ockham and Hume (E 64) most likely meant---is just the principle as stated without ambiguity by Aristotle. I think we should be wary of Aristotle's principle. Hereafter, I shall refer to it as the narrow mode of causality. Although it obtains throughout much of existence, it evidently does not obtain for physical processes in quantum regimes . . . . I suggest we reformulate the principle more broadly, thus: 'Identical existents, in given circumstances, will always produce results not wholly identical to results produced by different existents in those same circumstances'. Application of the law of identity to action or to becoming would seem to require only this much (contrary to Peikoff 1991, 14-15)." (25, emphasis added)