In the first place it is of some service to learn how and by what means all the Peloponnesians came to be called Achaeans.
For the people whose original and ancestral name this was are distinguished neither by the extent of their territory, nor by the number of their cities, nor by exceptional wealth or the exceptional valour of their citizens.
Both the Arcadian and Laconian nations far exceed them, indeed, in population and the size of their countries, and certainly neither of the two could ever bring themselves to yield to any Greek people the palm for military valour.
How is it, then, that both these two peoples and the rest of the Peloponnesians have consented to change not only their political institutions for those of the Achaeans, but even their name?
It is evident that we should not say it is the result of chance, for that is a poor explanation. We must rather seek for a cause, for every event whether probable or improbable must have some cause. The cause here, I believe to be more or less the following.
One could not find a political system and principle so favourable to equality and freedom of speech, in a word so sincerely democratic, as that of the Achaean league.
Owing to this, while some of the Peloponnesians chose to join it of their own free will, it won many others by persuasion and argument, and those whom it forced to adhere to it when the occasion presented itself suddenly underwent a change and became quite reconciled to their position.
For by reserving no special privileges for original members, and putting all new adherents exactly on the same footing, it soon attained the aim it had set itself, being aided by two very powerful coadjutors, equality and humanity.
We must therefore look upon this as the initiator and cause of that union that has established the present prosperity of the <a class="linkToPlace" target="_blank" href="/place?placename=Peloponnese&groupId=861&placeId=1552">Peloponnese</a>.
These characteristic principles and constitution had existed in <a class="linkToPlace" target="_blank" href="/place?placename=Achaea&groupId=272&placeId=533">Achaea</a> from an early date.
There is abundant testimony of this, but for the present it will suffice to cite one or two instances in confirmation of this assertion.
Walbank Commentary