The phrase "assumed alone" is correct and usable in written English.
It can be used in contexts where you want to indicate that something is taken for granted or accepted without any additional support or evidence, particularly in discussions or analyses.
Example: "The conclusion was reached based on the data assumed alone, without considering other influencing factors."
Alternatives: "taken alone" or "considered in isolation".
But unless the U.S. government seriously reconsiders its proposed self-damaging trade policy, its two partners should move forward to protect and lean on another line of defense — the World Trade Organization multilateral system — and leave the U.S. government to assume alone full responsibility for killing NAFTA.
What's more, though he took on the leadership role as a strategist, Johansson never assumed he alone had the understanding or the ability to form a global appliance strategy; he relied heavily on both corporate and local managers.
"The black hole, a type known as a quasar, sits 2.4 billion light-years from Earth and is so bright that astronomers have assumed it was alone in its area of space for decades," Brabaw explains.
While he was committed to the success of his subordinates, Andrew at some level assumed that he alone could meet his high standards, and as a result he was laboring under a competing commitment to maintain absolute control over his projects.
Sometimes people have a tendency to ignore the people standing alone, assuming that they must be alone because they aren't very important.
Although it's widely assumed that the president alone is empowered to decide what military option the United States should pursue in Iraq, that is not the case.
Knowing that deaf people suffered prejudice and inhumane treatment in Goodricke's time, some have assumed that he worked alone.
According to The Telegraph, Mayer -- who interviewed members of the Prince's inner circle -- details a moment on the night before his wedding when a "desperate" Charles reportedly told an aide, "I can't go through with it... I can't do it". He is also said to have confessed Diana was "not the jolly country girl he had assumed". Charles wasn't alone in his doubts about the relationship.
So we have to assume that money alone doesn't guide decisions about what to eat.
Hamadeh told the PM that he could not assume the risk alone for a showdown with Hizballah.
They did not assume that they alone had to bear the burden of motivating employees with inspiring messages.
