The above video by the professed atheist and YouTube user 'Venaloid' was recently brought to my attention, and I thought it was worth sharing and responding to. Venaloid admits that atheists cannot know that their thoughts and senses are trustworthy, however, he says it's a "double-edged sword" because Christians can't know that God isn't deceiving them, therefore he argues Christians can't trust their thoughts and senses either.
Venaloid's argument raises the same basic issues that I've already dealt with in my other post 'The Deceptive God Argument Refuted.' (Please read that article if you haven't already as I thoroughly refute the idea that God could be deceiving us.)
I've also dealt with this whole issue here in my FAQ section - How do you know YOUR reasoning is valid? And just below it in the same FAQ section: How do you know YOU aren't in the Matrix?.
Venaloid asks a few specific questions:
//Would God come down and tell you that your thoughts and senses are being deceived?//
He wouldn't need to because he's already revealed himself to us through the Bible and he's promised us that he cannot lie or deceive us.
//Why do we have delusional people?//
This is a separate issue. You know that you aren't in a mental hospital right now the same way I do - by revelation from God. The only difference is I profess to know this revelation from God and you suppress it. We have delusional people because we live in a fallen world where people get sick. This all goes back to Adam and Eve's rebellion against God.
So at the core of your worldview, you can't know if your reasoning is valid and able to bring you to proper conclusions about anything. You can't justify the reasoning of anyone - even the most sane person - from within your worldview.
In contrast, at the core of the Christian worldview, we know that we can trust our reasoning by revelation from God. This is because God made us in his image, and so our minds are basically reliable.