Let's explore this.
James 2:14 What good is it, my brothers, if someone says he has faith but does not have works? Can that faith save him? 15 If a brother or sister is poorly clothed and lacking in daily food, 16 and one of you says to them, “Go in peace, be warmed and filled,” without giving them the things needed for the body, what good is that? 17 So also faith by itself, if it does not have works, is dead.18 But someone will say, “You have faith and I have works.” Show me your faith apart from your works, and I will show you my faith by my works. 19 You believe that God is one; you do well. Even the demons believe—and shudder! 20 Do you want to be shown, you foolish person, that faith apart from works is useless? 21 Was not Abraham our father justified by works when he offered up his son Isaac on the altar? 22 You see that faith was active along with his works, and faith was completed by his works; 23 and the Scripture was fulfilled that says, “Abraham believed God, and it was counted to him as righteousness”—and he was called a friend of God. 24 You see that a person is justified by works and not by faith alone. 25 And in the same way was not also Rahab the prostitute justified by works when she received the messengers and sent them out by another way? 26 For as the body apart from the spirit is dead, so also faith apart from works is dead.
In western culture, there is often a very real dichotomy between what we believe and what we do. You can believe stealing is wrong, but if you accidentally get out of a store with a small item in the bottom of your shopping cart, you may not go back and pay for it. You can justify it with any range of excuses, but ultimately, you stole it. This represents a disconnect from what you believe. In ancient Greek culture (which all of the New Testament is in someway influenced by,) the spirit has a more direct connection to the body, and therefore, actions a more direct connection to beliefs. James is saying "I don't need to tell you how much faith I have, you can see it, you can see it in the dirt on my hands, you can feel it in the strength of my hug, you can see it in the smile on my face, you can hear it in the tone of my voice, you can tell in an unwavering way by the way I am."
Why is it today that it becomes increasingly difficult to tell the difference between Christians and the world? What is going on here? We live in a world that draws us to value the same things as the world, to love the same things, to believe the same things, to think the same things, to act the same ways. Why is our rate of divorce the same? Why are we spending our time arguing about gay marriage when there are people starving all over the world? Why don't people stop us on the sidewalk and say "you're a Christian aren't you?"
Check this out, it's like a math problem, verse 8 THINK, verse 9a DO and 9b FAITH.
Let me re-emphasize this because I know some of you are still stuck in the faith vs. works mindset. You are essentially equating think with faith. That is not how it was intended. Just as your spirit separated from your body essentially destroys what is "you" so separating the think and do parts of your faith destroys what faith really is. Faith is not a word attached to something you just believe. "I have faith that it will rain." Nor is it something achieved by performing a task. Faith is a thing that when it exists in a person, you should be able to see it before you are told about it.
The equation works both ways. If there is faith, there is think and do, if there is think and do, then there is faith.
So, do they know you are a Christian because of your love for one another?