How do we know that our purpose is not to be bad? Surely evil men have, by extension, caused some good. And even without that idea, we have no use what our purpose is on this earth -- how do we know that us being bad isn't part of the divine plan?
Or, put another way, how can it be both that God wants us to follow His will, and also evil/bad people be part of the divine plan?
Are there any sources that discuss this idea?
Devarim 10:12
יב וְעַתָּה, יִשְׂרָאֵל--מָה יְהוָה אֱלֹהֶיךָ, שֹׁאֵל מֵעִמָּךְ: כִּי אִם-לְיִרְאָה אֶת-יְהוָה אֱלֹהֶיךָ לָלֶכֶת בְּכָל-דְּרָכָיו, וּלְאַהֲבָה אֹתוֹ, וְלַעֲבֹד אֶת-יְהוָה אֱלֹהֶיךָ, בְּכָל-לְבָבְךָ וּבְכָל-נַפְשֶׁךָ
What does Hashem want from you? To fear the Lord your G-d, to walk in His ways, to love him, to serve the Lord your G-d with all your heart and all your soul
and many other such verses.
Hashem wants us to follow in His ways and serve Him.
Hashem does not want us to be evil and His plan does not necessitate such. He gives us free will and allows us to be evil. However, in His ultimate control, He weaves all of the choices that we make into His divine master plan, in a way that we cannot comprehend (Ramchal - Da'as Tevunos siman 54). In the time of Moshiach it will be revealed to us how everything fit in exactly to Hashem's plan, but while in this world we cannot comprehend it (ibid).
There is a basis for your question.
In the book Leshem Shevo V'Achlama (הקדו"ש דף כ"ט ע"א), Rabbi Shlomo Elyashiv zt'l brings the verse "I call heaven and earth as witness this day against you, that I have set before you life and death, blessing and cursing: therefore choose life, that both you and your descendants may live" (devarim 30:19)
He asks why does it say "therefore choose life". Isn't that obvious?
He answers by saying, really one might think that it doesn't matter since in the end everything will be rectified. Even if one chooses evil, the punishments he will get after death will rectify it all. Therefore, he says one might think either direction is ok, and the verse comes to teach you that G-d wants the way of good.
Well, there's this, from Likutei Eitzos, which serves as one partial answer to your question:
"That man has the evil inclination is really a great thing. Thus man can serve God with the very evil inclination itself. Even when he is exposed to the burning of the evil inclination, he can still strengthen himself even then and try to draw some of its passion into the service of God. If man had no evil inclination his service would be worth nothing. This is why God gives the evil inclination such power against men, especially those who genuinely seek to draw closer to Him. The onslaught of the evil inclination brings men to all manner of sin and devastation. But even so, in God's eyes all this is acceptable because of the preciousness of the gestures which people make when confronted by the full force of the evil inclination -- those gestures of fighting and escaping. In God's eyes this is more precious than if a person served him for a thousand years without the evil inclination. All the worlds were created only for the sake of man. The whole preciousness and greatness of man lies in the fact that he is confronted by this strong evil inclination. The more it arrays itself to attack, the more precious in God's eyes is every single gesture one makes to strengthen oneself against it. God Himself will send help, as it i s written: `The Lord will not abandon him into his hand' (Psalm 37:33) (Ibid.)"
