Simply, if you want to end an argument about the existence of God or “intelligent design”, ask a thinking person “how does it know?” with regard to our immune system – or any complex system within the human body, nature or the universe.
Ask them if the existence of one single planet with life (the would be Earth) in such a vast Universe of no-life doesn't seem a little unusual. If they say their could be another Earth-like planet, ask them if such scarcity still doesn't seem unusual -- and point out to them that they have entered into the realm of believing something totally unproven and without any evidence.
Then ask how human (or animal) consciousness is explained by the "Big Bang" or anything else in the physical realms of energy and matter.
The atheist can then start trying to explain things in terms of principles and mechanisms – none of which he/she can explain if you then ask how the parts know what to do or how their intelligence or “powers” came into being. The atheist may be able to explain what happens (which is amazing enough to convince most thinking people that there is a God), but they can’t reasonably explain how this system knows what to do or how it came into being without intelligent design. Case closed.
Everyone knows that stars, the Milky Way, other galaxies, black holes, etc. exist. How they all got here is another question, however. Atheist scientists and those who repeat what they hear from them, hang their hats on "Big Bang" and 'billions and billions of years' -- and then go on their merry way as if that actually explains much. They have taken a shot at 'what' but have done an even poorer job, however, of actually explaining how or why creation happened. Then they have the gaul of scoffing at those who give God the credit.
What people always skip over, even if "Big Bang" explains the macro-level of creation, is 'how in the World did some of the living nano-level "beings" ever come into being and 'how in the world' do they have any idea what they are doing and how they do it?
To make my point, simply go through the process below regarding some of the most amazing things in the Universe:
Step One: View this video from Kurzgesagt on the immune system https://www.youtube.com/watch?v=lXfEK8G8CUI (and/or https://www.youtube.com/watch?v=BSypUV6QUNw about complement proteins, phagocytes, membrane attack complex).
Step Two: Ask a “how do they know?” question about the existence and functions of seemingly brainless macrophages, neutrophils, complement proteins, dendritic cells, T cells, B cells, etc.
Step Three: Try to explain how likely it is that a system like this could “evolve” through random processes – even if they add the traditional atheist cop-out of “billions and billions of years” or “big bang” to their explanation.
“How does a single one of these cells know what to do?”
“How do each of these cells even know about the other cells on the team?”
“How do all of these cells know how to work together?”
The case for “no God” or “no intelligent design” should be closed once and for all. There is no way that a half-honest person could dismiss or explain away this incredibly complex system and the intelligence of its cell “agents”. These tiny cells have intelligence, functionality, communication and cooperation capabilities beyond belief. Each one is amazing – a miracle. Anyone will simply sound foolish if they try to explain away the incredible miracle of this system (and many others) in terms of random evolution, mutations or coincidence. Each cell is a miracle in itself – let alone the entire coordinated system of all of them working together.
As John McEnroe used to say, “you can’t be serious” if you try to claim that this kind of system could have just evolved through randomness. What are the odds? 100 billion to one? Trillion+? Now who sounds like they are taking things on faith? Now who sounds like they are making things up to fit their preconceived ideas?
While the examples above should be enough proof of intelligent design, there are thousands of other examples. Here are a few more where you can ask how they came into being.
Explain how two very explosive gases form super-safe water, how water has three states, and how it is so vital for life in “almost” every non-dormant cell. This is the easiest one until you ask why it (water) doesn't seem to exist in any useful quantities anywhere else. Surely there is lots of hydrogen -- and Oxygen shouldn't be too hard for a "Big Bang". Where's all the water?
Explain how light energy becomes mass and vice versa. Easy? Easy for Einstein, maybe, but even he couldn't explain the how or why. Who would have ever thought that matter could become energy -- and so much of it. What a great (intelligent) idea!
Explain the inner workings of gravity if you really want to talk about something unbelievable that could only exist if there was an intelligence beyond genius in the universe. Scientists still can't explain why it works.
Consider the “Standard Model” https://www.youtube.com/watch?v=2ynMmhqVGx4 This will blow your mind if you just think there are protons, neutrons and electrons in mass.
Consciousness -- one more time. Explain that.
So, just in case you encounter someone who "believes in science" and sees the world as simple Minecraft blocks/components that he/she or the "Big Bang" could slop together -- just ask why there is such a rarity of life in the Universe, how anything living was created, who created life, or “how do these nano-beings know” how to work together to make a living nano-world. Ask this person to explain the "Standard Model" and how that might have happened in terms of a "bang". Ask them to explain consciousness. Impossible after impossible after impossible -- right?
“’Nuff said”