public function has($class) {
		if (isset($this->singletons[$class])) {
			return true;
		}

		if (isset($this->aliases[$class])) {
			$class = $this->aliases[$class];
		}

		try {
			$this->getReflectionClass($class);
		} catch (Exception $e) {
			return false;
		}

		return true;
	}