on his immediate needs and disregards any concern for others.  After many men die, he continues to hide his secret and allows Steve to take the fall.  So, Miller paints Joe as both a tragic hero and a villain.

This is a great question, focussing on the ambiguity of this central character to the play. Your answer will want to focus on the presentation of Joe Keller in the play, and how, in a sense, he is a hero in what he has achieved in his life. Note how when we first are introduced to him Miller describes him in his stage directions as follows:

A heavy man of stolid mind and build, a business man these many years, but with the imprint of the machine-shop worker and boss still upon him. When he reads, when he speaks, when he listens, it is with the terrible concentration of the uneducated man for whom there is still wonder in many commonly known things, a man whose judgements must be dredged out of experience and a peasant-like common sense. A man among men.

There are a number of aspects to Joe Keller's character, but certainly we can see how is rise from labourer to owning his own factory that he manages is a heroic rise given his starting point. It is clear too that he is respected by his neighbours and the children of the neighbourhood, who almost treat him like some kind of surrogate grandfather, for example Bert.

However, the other side of this character which is gradually revealed is that his business success has only come at a cost - Joe Keller deliberately and knowingly produced faulty air plane engines which were used in fighter planes during the war and resulted in the death of 21 pilots. He blamed his partner and was acquitted of the crime, but during the course of the play he is forced to admit his culpability. Recognising that he was responsible for the death of not only his son, Larry, but for those pilots, as they were "all his sons," Joe sees no option but to kill himself.

Joe Keller grew up in poverty and was not able to attain much education. The Great Depression added to his fears of not having his material needs met. For him, his good job is all-important. He has an intense dread of being poor again, and he wants, above all else, to provide a good life for his family, with a nice home and steak dinners. He expresses his love through what he can give materially to his wife and children. A bit of the bull in the china shop, he doesn't think too hard about how he is making his money or if he should cultivate other values.

Joe has done well in providing for his family as a successful businessman. His tragic flaw, however, is placing too much importance on his job and financial success. He approves the sale of the cracked cylinder heads to the army even though he knows they are flawed because he wants to protect his job and family. He places his own security ahead of human lives.

Joe's vision is tragically narrow. Only the needs of himself and his family are real to him. The fact that other young men just like his sons are died as a result of his decision is not something he is capable of fully realizing until the end of the play.

Joe buys into a tragic version of the American Dream that says that material success is all-important, even more so than human life.