public function get($alias)
    {
        if (!isset($this->registered[$alias]))
            return false;
        
        // Does an instance exist for this alias?
        if (isset($this->instance[$alias]) && is_object($this->instance[$alias]))
            return $this->instance[$alias];
        
        // Execute the Closure to get the first instance
        $this->instance[$alias] = $this->registered[$alias]($this);
        if (!is_object($this->instance[$alias]))
            throw new Exception('The alias "' . $alias . '" does not return an object.');
        
        return $this->instance[$alias];
    }