Real Question about tires.

Would it be stupid to put two knobby tires in back and two road tires of the same dimension up front? I have one bad tire and three worn tires.

I feel like buying one new tire is weird and I don't want to buy 4 new ones.

So my plan is to buy two new tires, road style, put them up front and run the knobbys in back.

Is this mental?