Achilles is the only mortal in the Illiad to experience uncontrollable rage.

Achilles is distraught when he learns of the death of his friend Patroclus.

At one point achilles had Post Dramatic stress disorder because he killed so many men.

According to the Homers Iliad,Achilles was the only one of the all other Greek warriors of the Trojan War truly focused on getting the best deal out of that business. Iliad ends with Achilles concluding the best ever deal that could have come out of that War; the exchange of the Hectors body for the very treasure of Troja.It is only a human thing to consider a war as another form or way of doing business in purpose of becoming ever more powerful. Only a human can look for, aim for, or expect for such a profiting business out of a bloody war.

Looking more closely at Homers Iliad (especially from this angle)it seams that this was the Achilles calculated canning and purpose on that war.

In my opinion one of the core themes of the Homers Iliad is the portraying of the dark side of humanity through the two of the most important human heroes of the Iliad , Hectors and Achilles.They both did what they possibly could do, regardless of the consequences to themselves or others.

It portrays the human canning and genius at the most over reacting and out of self control.

Only through a human can a human value and attribute be best displayed or portrayed, even in the case of a poem like the Homers Iliad,I think. :-)