Can I activate an iPhone 5s that is bought unlocked from Apple?

I'm planning on getting an iPhone 5s in the near future. If I buy it unlocked from the Apple site, and it has no SIM when it arrives, can I activate it without the SIM? Use the phone without a SIM inside?

No, you will always need a SIM to activate.

https://discussions.apple.com/...0?tstart=0

You can remove it though after activating and use the phone.