Paul is going to contrast two very different ways of living. The first way is the way of the “flesh.” It’s reference to our selfish sinful nature. We are all born with one of these. I know we don’t like to think so and many views today focus on the basic “goodness” of man. Yet, it’s unavoidable. Jesus often encountered people who thought they lived up to God’s standards. Jesus would then remind them of their true position by pointing out the 
sinful nature was in all of us. He’d instruct the righteous religious leaders who knew very well the law against adultery and he’d explain that standard. Anyone who had impure thoughts and lusted after the flesh in their hearts was guilty of violating that law. That changes the way we see ourselves, doesn’t it? He said that we know it’s against God’s law to murder, but anyone who hates someone is guilty of violating that standard. Doesn’t that change things a little? It certainly does with me. I hope it does with you too.
The focus of our sinful nature is always on self-gratification. In Galatians 5:19-20 Paul says, “Now the works of the flesh are evident: adultery (some texts omit this one), sexual immorality, impurity, sensuality, idolatry, sorcery, enmity, strife, jealousy, fits of anger, rivalries, dissensions, divisions…” Any honest person must see themselves in at least one of these. And Paul had already made it clear that if we fail at one point of the law, we’ve failed the whole law. You might remember back in Galatians chapter 3, Paul explained the purpose of the law as being that which showed us ourselves in all our sinful glory.
When writing my devotions on chapter 3 I spoke about the dentist’s mirror. He sticks it into our mouths and with the mirror he sees what’s wrong with our teeth. But he doesn’t use it to drill out the decay nor to pull a rotten tooth nor to insert a filling into the cavity. All it can do is show him what is wrong. It can’t do a thing to remedy the problem. That’s the law. Paul’s list of the “works of the flesh” do nothing to cleanse us from our sinful condition, it merely points it out. This is how Jesus used the law and I believe that this is how Paul is using it as well. The “law” leaves us at the mercy of our sinful natures, but there is another way to live. There are “works” of the flesh, but there is also a fruit (singular) of the Spirit.