See The Teleological Significance Of The Entity From "potential-achievement"

Aristotle uncovered the meaning of "substance" by distinguishing two meanings of"being",to be some attributes and to be the thing itself.By this distinguishing,Aristotle cleared that the attribute is predicated on the thing itself,i.e.substance.According to the meaning of substance,what can be a thing's substance is the form,matter or the composition of the two,and the form can be seen as essence,the universal or the genus.To the relationship of the form,matter and the composition,Aristotle stated that the form and matter are not two things which can be separated apart from each other on the contrary,the form is potential in the matter and becomes reality by matter.Thus,matter,form and the composition are just one thing.In this term,the form means individual,not universal.Matter can't be a thing's substance.For it don't have the meaning of either the attribute or the essence,which means that matter can't be a subject.In the sence of substance,the form is prior to matter and the composition,so a thing's substance is its form,which means the essence.To what the essence,we can't always say it is the thing itself,which can't help us understand substance more.For this reason,we needs to understand the essence as a reason,which makes matter be a thing like this.It needs to use the structure of "potency-actuality" to explain that how the form could be a thing's reason.Saying a thing has such potency is meaning that this potency must be actualized when it could actualize.Actuality has the meaning of reality.Thus,things can exist as a structure of "potency-actuality",in which substance would be a reason as a prior purpose on ontology,generativism and in the thing's specific movement.On ontology,the form as a purpose is the reason why matter appears like this.Saying a thing is to be is saying that the matter is actualizing to the form,which is prior not being made.On generativism,all generating process can be described as a structure of "form-matter-the generated",in which the form is prior and as a purpose that matter actualize to the generated.In the things' specific movement,the form means the function expressed in the movement,and the movement is actuality to the form.What's more,in the sense of the thing's good and bad,truth and falsity,a thing is bad only in its specific being,i.e.the potency's specific actualizing.A thing's form is just the thing's good,so that a thing can't deviate its form.A thing can be judged only in attributes.The form is always true,and only can be known but not judged.All these indicate the priority and finality of the form as purpose.Aristotle's exploring about the purpose of specific substance must lead to that of the highest purpose,which is the totally actualized good,i.e.a kind of prior natural order.