At the same time, however,

然而与此同时
there are limitations in Piaget's theory.

皮亚杰的理论也有其局限之处
Some of these limitations are theoretical.

有些局限是理论上的
It's an interesting question

问题是
as to whether he really explains

他是否真的解释了
how a child goes from a concrete thinker to an abstract thinker,

儿童思维是如何从具体向抽象转变的
or how he goes from not having object permanence

或是真的解释了
to understanding object permanence.

儿童的客体永存性概念是如何从无到有的
There's methodological limitations.

还有些研究方法上的局限
Piaget was really big into question and answer,

皮亚杰非常热衷用问与答的方法进行研究
but one problem with this is

但这里存在的一个问题便是
that children aren't very good with language,

儿童并未能完全掌握语言