Using a functor in a generic function

I have built a generic function which takes a certain container (using an Iterator for its beginning and end) and a Predicate (functor which serves as a some sort of condition check) and counts the number of pairs in that container which are true in the Predicate condition. As the following

//Counts number of pairs in a container that follow the rule of the Predicate
template <typename Iterator, typename Predicate>
int countPairs(const Iterator first, const Iterator last, Predicate pred){
    int counter = 0;
    for(Iterator current = first; current<last; ++current){
        Iterator next(current);
        for(++next; next<last; ++next){
            if(pred(*current, *next)){
                counter++;
            }
        }
    }
    return counter;
}

Then, i wanted to use the generic function in order to examine whether a certain vector is sorted. So i've built the following 'Predicate' which checks whether a pair of numbers is sorted:

bool isBigger(int a, int b){
    return b < a;
}

Then, i've built a function called which basically uses the two above in order to take a vector and check if its sorted:

bool isSorted(std::vector<int>& v){
    int size = v.size();
    if(size == 0 || size == 1){
        return true;
    }
    return countPairs(v.begin(), v.end(), isBigger()) == 0;
}

When I try to build, if provides me with the following errors:

error: no matching function for call to 'isBigger'

note: candidate function not viable: requires 2 arguments, but 0 were provided

I'm pretty sure its because of the way i've used isBigger function in the countPairs calling. But that's how generic code works no?

Thank you very much.