I'm saying that mankind can be good just by their own intellect or reason!!
God gave us those tools in order to:
1- recognize His Signs and Warnings
2- choose to follow His Guidance and Prophets
3- be able to accept that not everyone is like us
He is the only Sovereign and we are His servants. We are not to make up our own rules about what is right or wrong. My emphasis on us being able to do good by ourselves is in relation to not needing an external force to insight us to do good, as my Christian friends argue is the role of the Holy Spirit. Unless I understand it wrong.
Guidance has come from God to every nation on earth. Is He to leave His beloved creatures without criteria and rules yet judge them all? Nay! All people have received their prophets, throughout history.
It's obvious we're not gonna know about all of them. It's no secret taht every prophet has had to put up with fierce resistance from the people he was sent to Enlighten. Only a few righteous men and women followed these prophets. But the societies either got rid of the prophet or "struck his name off the record", never to be heard of a again.
So every society has received Guidance. Every nation has gotten its way of worship. Some were preserved, others corrupted and sank back into idolatry and pagan beliefs. It is a Sign of God's infinite Wisdom and Knowledge that He has created so many varieties of things, especiall humans!
O mankind! Lo! We have created you male and female, and have made you nations and tribes that ye may know one another. Indeed! the noblest of you, in the sight of God, is the best in conduct. Lo! God is All-Knower, Fully-Aware. (Quran 49: 13).
And of His signs is the creation of the heavens and the earth, and the difference of your languages and colours. Lo! herein indeed are portents for men of knowledge. (Qur'an 30:22)
Before Adam was cast down to Earth from Paradise, he was forgiven for his disobediance of God's Command regarding the 'Tree'. (in our version, Adam and Eve were both deceived by Satan; not Eve being deceived then bringing Adam down with her)
Then Adam received from his Lord Words. And his Lord pardoned him (accepted his repentance). Verily, He is the One Who forgives (accepts repentance), the Most Merciful. God said: "Get down all of you from this place (Paradise), then whenever there comes to you Guidance from Me, and whoever follows My Guidance, there shall be no fear on them, nor shall they grieve." (Qur'an 2:37-38)
God Loves His creatures and would not let us get lost on this Earth. He constantly and consistently sent us Warners and Messengers from Him. All societies have had their fair share. Every nation will be judged by what God has sent to it.
Verily, We (God) did send down the Torah [to Moses], therein was guidance and light, by which the Prophets, who submitted themselves to God's Will, judged the Jews. And the rabbis and the priests [too judged the Jews by the Torah after those Prophets] for to them was entrusted the protection of God's Book, and they were witnesses thereto. Therefore fear not men but fear Me (O Jews) and sell not My Verses for a miserable price. And whosoever does not judge by what God has revealed, such are the Kâfirûn (i.e. disbelievers) (Qur'an 5:44)
Let the people of the Gospel judge by what God has revealed therein. And whosoever does not judge by what God has revealed, (then) such (people) are the Fâsiqûn (i.e. rebellious/disobedient) to God. (Qur'an 5:47)
NONE OF US should make up his own rules or rely on 'self-goodness' alone. But we must follow the guidance that God has sent down to each of us.
My argument about 'self-goodness' is that we work good deeds by ourselves, without the need for a Holy Spirit/Ghost to work through us. Humans have been able to do good since day 1, before the Holy Spirit entered us.
We must use our intellect to ponder about God, our reason to see His Guidance and Magnificence, our freedom of choice to choose to follow His guidelines for a better life.
I remember someone said that Jesus was the only human without sin and he set an example to all of us. I have to agree and disagree on this one. Yes, he was without sin and set an amazing example for all mankind. But he wasn't alone in this. All the prophets were without sin, by definition a prophet of God is a man without sin. And if he sins, God can remove his sins and pardon him in no time.