Certainly it can't be denied that Jerusalem is, to all intents and purposes, the seat of Israel's Government and judiciary. And it has been almost since the creation of the Jewish state in 1948.
But in a city as ancient and complex as Jerusalem, there is more than one "reality".
And here is why the situation is far more complicated:
Jerusalem is not only a Jewish city
About one in five Israelis are in fact Israeli Arabs — effectively Palestinians who have Israeli citizenship.
And beyond the "green line" that separates Israel from occupied territory, Palestinians still make up much, if not most, of the population in East Jerusalem.
For them, it is unthinkable that their own capital in a future state could be anywhere but Jerusalem.
Jerusalem is sacred not just to Jews
The old, walled city of Jerusalem is sacred not just to Jews, but equally to Muslims and Christians.
The Western Wall pre-dates both Christianity and Islam. The Church of the Holy Sepulchre is where Christians believe Jesus was crucified.
And the Al Aqsa mosque and famous gold-roofed Dome of the Rock represent the third most holy site in the world for Muslims, after Mecca and Medina.
Although Israel controls access to the Temple Mount, above the Western Wall, an Islamic trust known as the Waqf retains authority over the Muslim holy sites.
Indeed, so volatile are the sensitivities over the site, Jews allowed onto the Temple Mount under strict controls are banned from overtly praying.
The sight of Jews even bowing their heads in prayer has led to violence in the past.
The UN hasn't recognised Jerusalem as Israel's capital
The United Nations has never recognised Jerusalem as Israel's capital because of its historical importance to other religions.
In its 1947 plan on partition, the UN divided the holy land into two nations — one for the Jews and one for the Arabs — but deliberately left Jerusalem out of the equation as a special international entity in recognition of its shared religious importance.
Foreign governments, in recognition of international law, have in turn refused to recognise Israel's sovereignty over Jerusalem, unless or until the city's status is decided through formal peace negotiations.
More than 150 nations, including Australia, maintain their diplomatic missions in Tel Aviv.
None appear ready to follow Mr Trump's decision.
The Arab half of the city is seen as occupied territory
Israel captured the Arab half of Jerusalem (as well as the West Bank) from Jordan in the Six-Day War of 1967.
Under international law, that land remains occupied territory.
The UN does not recognise Israel's right to the land.
Palestinians have laid claim to Jerusalem
Palestinians have long laid claim to Jerusalem — Al Quds in Arabic — as their own capital under a possible two-state solution.
But since Israeli occupation, the Palestinian seat of government has been in the West Bank city of Ramallah, a half hour's drive from Jerusalem.
And that's not all …
The other "reality" too, of course, is that the two-state solution is an impossible goal.
The changing facts on the ground mean there is no longer a contiguous land for Palestinians to create their own state.
And the status of Jerusalem is just one of four "core issues" that have stood in the way of a peace agreement.
The remaining three pose their own set of challenges.
The settlements are here to stay
Palestinians want a future state to include all of Gaza, and the West Bank land they inhabited before the 1967 war.
But in the half century since, around 500,000 Jews have moved into expanding settlements in East Jerusalem and the West Bank.
One of the largest such settlements, Ariel, is a town of at least 20,000 Jews deep inside the West Bank.
These settlements are also deemed illegal under international law.
But Palestinian leaders are dreaming if they think Israel will agree to give them up in return for a peace deal, no matter how much the Israeli Government professes to support a two-state solution.
There are 5 million Palestinians with nowhere to go
An estimated 5 million Palestinians live in refugee camps in the West Bank, Gaza and neighbouring countries including Jordan, Lebanon and Syria.
Most are today descendants of Palestinians who fled their homes during or after the 1948 Arab-Israeli war.
Palestinian negotiators demand the right of all refugees to return to their original homes inside Israel.
Such a proposition is impossible.
Israel — an avowed "Jewish state" of barely 9 million people — will never accept 5 million Palestinians into the country.
But with many refugees denied full rights in neighbouring countries, their fate continues to thwart peace efforts.
Israel wants to keep troops on the border with Jordan
Israel insists a peace agreement allows it to maintain a military buffer zone along the border between Jordan and the West Bank.
The deployment of Israeli troops to the area has forced many Palestinians out of their homes.
Palestinian negotiators have refused to accept any Israeli military presence on the land of a future Palestinian state.
In his announcement on Jerusalem, Mr Trump may think he has resolved one of the most intractable issues at the heart of the conflict.
Time will tell if he is right.