Aristotle starts with the acceptance of the fact that every human being is a social being and then continues by defining the structure of the little town (κώμη) and that of town (πόλη). The main argument is that: Altough the opinion of every individual could be wrong, the total combined opinion of the many people is always better than the opinion of a single, even wise man. Thus, Aristotle promoted the existence of the middle class, as a best ratio between oligarchy of the rich and ochlocracy of the poor.

Demetris, thanks for your answer. I think we are talking about powers in a different sense. I mean the causal powers that Aristotle (and others) have posited as 'causing' perception, etc.

I think the simple meaning of power can be derived from Aristotle analysis and his logic in different circumstances between individuals and rulers . 

Asaad, can you provide an example of what you mean?

Power (or being-in-potency or potency, as it is more typically called by Aristotelians) has real being, but stands between nothingness and being-in-act. For example, a match has the potency to light on fire if struck.

The potencies a thing has are grounded in its actualities. It is because of what a match actually is, and its actual characteristics, that it has the potential to light on fire if struck.

The purpose of the theory of act and potency is to overcome Parmenides' argument that change is impossible. Parmenides held that change must entail being coming to be from nothing, but this cannot occur because from nothing nothing comes. Aristotle concedes that something cannot come from what is strictly nothing. So, to overcome the paradox, he posits a kind of being that is real, albeit occupying a status between the actual and non-being. Change involves one kind of being (act) coming from another kind of being (potency).

I suppose I did not really define potency, but is this a helpful description?

Hi Marcus, yes, what you say is very succinct and helpful. I appreciate your comments. What you say confirms my understanding of powers but when these become power ontologies I find the concept a little more difficult. 

HI paul

hope these help :

http://pubpages.unh.edu/~cewitt/Site/My_Philosophical_Life_files/Aristotelian%20Powers.pdf

http://www.philosophy.ox.ac.uk/__data/assets/pdf_file/0020/32375/Causation_without_glue_-_Aristotle_on_causal_powers.pdf

"In a nutshell, causation is the fulfil- ment of an agent’s causal powers in what is acted upon. The realization of the agent’s power occurs in dependence on coming in contact with a passive power, on which the active power operates''

I think your reading of individual power is very different to Aristotle's metaphysical powers.

The target of your question is somewhat unclear, as is indicated by the rather diverse reactions of other respondents. Are you asking for a "simple definition" of dynamis (δύναμις),: the term that Aristotle uses for potency, potentiality, capacity, power, where the translation (into English, say) depends upon the context? As you list your topic as "metaphysics", dynamis would be the most likely candidate for the thing for which you hope to find a simple definition. If so, then there is no one simple definition to be found, but there are several definitions, as is so often the case for Aristotle's key systematic terms, since these are, according to him, typically polysemous. The normal place to start looking is in Metaphysics V — Aristotle's own "dictionary" of key terms. That doesn't always provide what you want, since the dictionary is not always in accord with what Aristotle says elsewhere. Moreover, the definitions provided may be difficult to fathom without reference to the larger discussions where the terms in question are deployed. But, if you are in fact interested in "power" in the sense of dynamis, then you will find Aristotle's own definitions in Metaphysics V, beginning at 1019a15. What he says there, in Tredennick's translation, is this:

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[1019a] [15] "Potency" [δύναμις] means: (a) the source of motion or change which is in something other than the thing changed, or in it qua other. E.g., the science of building is a potency which is not present in the thing built; but the science of medicine, which is a potency, may be present in the patient, although not qua patient. Thus "potency" means the source in general of change or motion in another thing, or in the same thing qua other; [20] or the source of a thing's being moved or changed by another thing, or by itself qua other (for in virtue of that principle by which the passive thing is affected in any way we call it capable of being affected; sometimes if it is affected at all, and sometimes not in respect of every affection, but only if it is changed for the better). (b) The power of performing this well or according to intention; because sometimes we say that those who can merely take a walk, or speak, without doing it as well as they intended, cannot speak or walk. And similarly in the case of passivity. (c) All states in virtue of which things are unaffected generally, or are unchangeable, or cannot readily deteriorate, are called "potencies." For things are broken and worn out and bent and in general destroyed not through potency but through impotence and deficiency of some sort; and things are unaffected by such processes which are scarcely or slightly affected because they have a potency and are potent and are in a definite state.

Since "potency" has all these meanings, "potent" (or "capable") will mean (a) that which contains a source of motion or change (for even what is static is "potent" in a sense) which takes place in another thing, or in itself qua other.

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And there is more of interest in the immediately following text. However, if you seek really to understand Aristotle's idea of a dynamis in the sense of a power to affect (or, for that matter, to be affected ) then you will want to look at his insightful discussion in Metaphysics IX, starting at 1046a1.

If you want to connect up the notion of a "power" with larger issues of causation and agency, you might like to read (among other things) my article, "Agency and Patiency — Back to Nature?" (Philosophical Explorations 5:1 (2002) pp. 59-81). At any rate, a "simple definition" of dynamis will not, by itself, get you all that far.