If God does not exist then all things would be permissible.

Without the existence of God each person can do what is right in their own eyes.
It would not matter if you lived a good life or a bad life because in the end of life each person would be equally dead, and there would be no God to give an account to or divine judgment when one dies. With this in mind, it brings us to a place where there are in fact no moral obligations in life to follow; considering that all morals, empathy, and even love would be nothing of what we ought to do, and in fact we would not know any better. For an atheist to be under any kind of moral obligations, empathy, or love would truly mean that they are following imaginary duties in life. With this in mind, if God does not exist, then at one time in history someone imagined and fabricated morals, empathy, and love. Therefore they are all manmade imaginary duties in life that with the absence of God/Lawgiver of all morals, empathy, and love there is no human obligation to any of these actions at all. Thus, this would mean all moral obligations in life have been manmade and these things we practice have no more meaning behind them then a manmade soda can.  
Throughout history there has been thousands of so called gods. In fact, people have made a god of their own image that is suitable for them. But what separates the Christian God of the bible from the thousands of counterfeit so called gods is that the God of the bible is uncreated. 

With this in mind, atheists do not want to accept God as an uncreated being, which proves that God could not have been imagined and made by mankind. What also separates God from the thousands of so called gods is that all other gods are limited to time and space, had beginning and ends. However, God is everlasting to everlasting, and He had no beginning and will never have an end, He has always been there. Our everyday experience of life doesn't allow us to grasp that too easily.

Our created minds cannot fathom an uncreated being such as God, who is eternally infinite. The fact that your created mind cannot stretch this far to fathom such a being of God implies that mankind is not the original source of God nor could have God originated from human beings. 

With this in mind, God as "that which nothing greater can be conceived," and is greater than all other thousands of so called gods would be the
correct answer for life.

Attributes Of God

(1) Total Independence: God does not need nor depend on anything to survive. God self-exists eternally, and has no beginning and no end.

(2) Unchangeable: God’s character cannot and does not change.

(3) Eternal: God exists forever.

(4) Unity: God is three persons, God the Father, Christ Jesus, the Holy Spirit, and the three are one true being.

(5) Spirituality: God is not made of matter, has no parts or dimensions, and has no limitations.

(6) Omniscience: God is all knowing.

(7) Omnipresence: God is all present all the time.

(8) Omnipotence: God is all powerful.

(9) Infinite: Without limitations.

(10) Incomprehensibility: Our human minds cannot fathom His eternal power.

(11) Immeasurable: God existence cannot be calculated, and expands beyond time and space.

(12) Impeccability: Unable to sin or do evil.

(13) Sovereignty: God has absolute control over the universe and grants mankind freewill.

(14) Inexplicable: We have no idea how big and great God is. God is so great that you can spend all eternity with Him, and never stop learning about Him.

(15) Holy: There is nothing and no one else as pure and perfect as God.

Ps 90:2, Ps 147:5, Ps 99:9, Ps 139:7-12, Luke 1:37, Luke 12:7, Isaiah 40:28, Job 42:2, Job 37:16, John 3:20, Rom 11:33, Col 1:16-18, Rev 1:8, Malachi 3:6