1.speculate的基本意思是“思索”“猜测”,指考虑或谈论某事而前提不确定或不完整,只是凭空猜想或仅凭推理,因此其结论往往具有假设性或理论性,本词强调推理过程。
2.speculate可用作及物动词,也可用作不及物动词。用作及物动词时,常接that从句。

speculate about(v.+prep.)
思考关于… think about sth
▲speculate about sth
We should speculate about the purpose of life.我们应该想想人生的目的。
It was a quiet evening and Tom was speculating about the origin of the universe.静悄悄的夜晚,汤姆在思索着宇宙的起源。

speculate in(v.+prep.)
投机 buy or deal in goods
▲speculate in sth
He made a fortune speculating in tin shares, and lost almost all of it in cocoa futures.他做锡股的投机生意发了财,在做可可的期货交易时几乎又赔了个精光。

用作不及物动词
▲S+～(+A)
We don't know all the circumstances, so it would be pointless to speculate.我们不了解所有的情况,妄加推测是没有意义的。
用作及物动词
▲S+～+that-clause
He speculated that he would succeed.他推测他将成功。
The police are speculating that this incident may be linked to a similar attack two weeks ago.警方推测这次事件可能同两周前的类似的袭击有联系。