Gone to Mars

OK, so Callie really likes to go outside, she enjoys it. Buddy still enjoys chasing her throughout the house. So today, when I opened the door to let Callie out, Buddy chased her right out the front door. When he realized what he had done he stopped dead in his tracks. I held the door open and told him to come back in, but he looked at me like I had two heads!!! Then he ran and hid under the truck. I kept trying to coax him into the house, and he did his “stretching cat thing” where his back feet stay in one place and he front ones advance. He got close to the front door, then ran back under the truck. So… I gave up on him and closed the door. Then, I went to the back door, opened it and whistled for him (yes, they humor us with some dog attributes just to keep us happy) and here comes this little black and white bullet cat from around the other side of the house! He comes flying into the dining room and looks at me and starts to tell me… “Mom… I was outside and some strangers were trying to make me come in their house… I was scared… but I didn’t go in… then you called me and I came right away… they didn’t get me!!” How do I tell his poor creature that it’s OK to go out that door… it’s the same big world, it’s NOT Mars. He panics if you put him outside from the front door, and he worries about Callie when she goes out that way. If he sees her go out that way, he sits by the door for a long time after she goes!!! How did we ever become cat people???