public function config( $key, $value = null ) {
		if ( is_array( $key ) ) {
			foreach ( $key as $id => $val ) {
				$this->config( $id, $val );
			}
		} else {
			if ( ! is_null( $value ) ) {
				return $this->bind( $key, $value );
			}

			if ( $this->bound( $key ) ) {
				return $this->make( $key );
			} else {
				$default = $this->get_default_config();
				return isset( $default[$key] ) ? $default[$key] : null;
			}
		}
	}