The way that Equation 2.2 works is , if the value of one of the classes score approaches 1 or 0 , the value of the whole equation approaches -infinity. The largest possible value(larger is what the generator wants) that Equation 2.2 can take is when the discriminator is completely unsure about what class the input belongs to, i.e. every term in the summation has the same value. **This makes sense **because its not possible to properly classify the input image into existing classes, so it must mean that it is its own new class.