(CNN)Ben Carson fielded national security questions Thursday night, where he warned of "bad apples" among Syrian refugees seeking asylum in the U.S., and he described how many troops he would be willing to commit to defeat ISIS.
Ben Carson tones down Syrian refugee rhetoric: 'bad apples'
"As many as needed and not one fewer," he wrote, during a Facebook Q&A.
The GOP presidential candidate also weighed in on the refugee debate, using an anecdote from his childhood about picking fruit with his family and learning to spot bad apples as a metaphor for screening refugees.
"When our government admitted that there is no way to screen these adult refugees for bad apples, I couldn't believe it," Carson wrote.
Carson earlier in the day compared the effort of screening refugees for terror connections to parents protecting children from rabid dogs.
"If there's a rabid dog running around in your neighborhood, you're probably not going to assume something good about that dog," Carson said in Alabama. "And you're probably going to put your children out of the way. That doesn't mean that you hate all dogs."
Carson used the Facebook Q&A to criticize the government's handling of ISIS, answering a question about how to defeat the terrorist group by writing, "Only in Washington is this a tough question."
"First you have to start trying," Carson wrote. "Not try to sound tough and stick your head in the sand. We need to do everything we can. Use every tool we have to execute certain and swift victory."