Cast generic type to object [duplicate]

Why is the compiler saying it cannot cast a generic type to object? I thought all objects were convertible to object. Is this possible?

https://dotnetfiddle.net/jFW4d0

using System;
                    
public class Program
{
    public abstract class Specification<T> where T : class
    {
        public abstract bool IsSatisfiedBy(T entity);
        
        public Specification<object> ToObject() {
            return (Specification<object>)this; // Compilation error (line 10, col 11): Cannot convert type 'Program.Specification<T>' to 'Program.Specification<object>'
        }
    }
    
    public static void Main()
    {
        Console.WriteLine("Hello World");
    }
}

Specification<T> is a type. Specification<object> is another different type. The code is attempting to cast a Specification<T> to a Specification<object>

• this is the cast that the compiler is referring to
• this cast is not the same as casting T to object