This is a complex question with much going on in deeper levels. What does it mean to "live"? Just to exist, or to find great meaning in one's existence? To breathe in and out, heart beating, mind thinking? Or is living something deeper and more spiritual? And what does "without God" mean? That He doesn't exist at all, or that He isn't an integral part of life? Scientists define "life" by several factors: existence, growth, ability to respond to stimuli, self-maintenance, and the ability to reproduce. According to these criteria, do we need God to live?
Can man live without God?
On the surface, the question is simple: could life (plant, insect, human) have come into being without the influence of a sentient, outside, extra-physical force? Of course, this question has been argued for centuries, both sides alternating between extolling their view and condemning the other. Those discussions can be found elsewhere. According to the Bible, God is the cause of all aspects of life. John 1:3 explains that God caused us to exist: "All things were made through him, and without him was not any thing made that was made" (see also Genesis 1; Psalm 139:13). Also, 1 Corinthians 15:42-49 promises complete, imperishable life in the future. Colossians 1:17 says that God maintains creation—"And he is before all things, and in him all things hold together." Psalm 104 vividly describes how God both maintains life on earth and causes it to grow (see also Genesis 1:29-30; Psalm 41:3, 65:10, 92:12; Matthew 5:45). God gave humanity the ability and responsibility to respond to stimuli in Genesis 1:28: "… fill the earth and subdue it, and have dominion over the fish of the sea and over the birds of the heavens and over every living thing that moves on the earth." And He not only charged us to reproduce (Genesis 1:28a), He controls our fertility (Genesis 20:18, 29:31, 30:22; 1 Samuel 1:5-6).
According to the Bible, then, God is clearly involved in every aspect of life. But most people consider life to be more than a physiologically animated condition. They want something more intangible, spiritual, like purpose and a connection to others outside of themselves. The Bible teaches that only God provides spiritual life (John 3:16). In John 10:10, Jesus says, "… I came that they may have life and have it abundantly." 2 Corinthians 3:18 promises we will grow in this life—"And we all, with unveiled face, beholding the glory of the Lord, are being transformed into the same image from one degree of glory to another. For this comes from the Lord who is the Spirit." Jesus promises that He will maintain this spiritual life in us: "I give them eternal life, and they will never perish, and no one will snatch them out of my hand" (John 10:28). His empowerment allows us to respond spiritually (Galatians 5:22-23). And He gives us the power (John 20:21-22) and the authority (Matthew 28:19-20) to reproduce this spiritual life. God is necessary for spiritual life. John 1:4 says of Jesus, "In him was life, and the life was the light of men." Full, meaningful life is only found in Jesus.
We cannot influence whether God is necessary for physical life—He either exists or He doesn't; He's either directly involved, or He isn't. But many do attempt to find spiritual life without God—in fact, the wisest man in history tried. Without the power of the Holy Spirit, however, he had to try to find spiritual meaning in physical things. Solomon couldn't create himself, he couldn't bring himself into existence, but he could easily see how out of his control existence was. Ecclesiastes 3:19 says, "For what happens to the children of man and what happens to the beasts is the same; as one dies, so dies the other. They all have the same breath, and man has no advantage over the beasts, for all is vanity." Ecclesiastes 2:3-10 describe how Solomon tried to grow by multiplying what he thought was life—riches, food, pleasures, even the beauty of nature. But in verse 11, he says, "Then I considered all that my hands had done and the toil I had expended in doing it, and behold, all was vanity and a striving after wind, and there was nothing to be gained under the sun." Solomon did find that he could spiritually respond to this spiritual life, but it wasn't the kind of response any of us would find attractive—"So I hated life, because what is done under the sun was grievous to me, for all is vanity and a striving after wind" (Ecclesiastes 2:17). Solomon had a lot to say about work—the vehicle by which we maintain our lives. In Ecclesiastes 2:22-23 he says, "What has a man from all the toil and striving of heart with which he toils beneath the sun? For all his days are full of sorrow, and his work is a vexation. Even in the night his heart does not rest. This also is vanity." He also sought to maintain his spiritual life through wisdom (Ecclesiastes 2:16), but quickly realized that even wisdom doesn't guarantee a fulfilled existence. Finally, he found that reproduction without God feels more like being robbed than leaving a part of oneself for posterity. Ecclesiastes 2:21 says, "because sometimes a person who has toiled with wisdom and knowledge and skill must leave everything to be enjoyed by someone who did not toil for it. This also is vanity and a great evil."
Solomon sums up his findings in Ecclesiastes 2:24-25: "There is nothing better for a person than that he should eat and drink and find enjoyment in his toil. This also, I saw, is from the hand of God, for apart from him who can eat or who can have enjoyment?" The wisest man who ever lived discovered that the simplest things in life—eating, drinking, and working—are only profitable if we include God.
Why did God create humanity?
What does it mean that humanity is created in the image of God?
Does humanity truly have free will?
What is human nature?
What is the Truth about salvation?
Truth about Humanity