An oath is a formal declaration or promise to carry out an action or maintain a pledge. Many oaths call on God or a sacred object to act as a witness and most involve allegiance to a person or cause. Oaths are made all over the place, many in a legal context. Such is the nature of the oaths which our MPs, military personnel (except the Royal Navy!), police officers and other public officials must make to the Queen. As the Republic group points out it is a complete affront to the spirit of democracy that our elected representatives have to swear allegiance to an unelected monarch. Here is the oath which our MPs must take.
I (MP name) swear by Almighty God that I will be faithful and bear true allegiance to Her Majesty Queen Elizabeth, her heirs and successors, according to law. So help me God.
There are some variations which can be taken, such as a non-religious equivalent, but the substance is the same in all cases. Note that until they take the oath they cannot represent you or I and do the job for which they were elected. As I have pointed out earlier, this has been, and still is, a problem for some Irish political parties.
There are two things to note about the oath. Firstly is the assumption that the monarch embodies the state in person and thus represents us all in a kind of social contract. The fact is that this is a constitutional figment which has been abused for centuries is beyond dispute (see here,paragraph 3). The difference is that whereas in previous centuries this abuse has taken the form of political or military oppression, in modern times this privilege takes the form of protections for private interests, such as mineral rights.
But there is something even more invidious about the Royal Oath taken by Members of Parliament which often goes unnoticed. Notice that the oath is to Queen Elizabeth, her heirs and successors. But since the Seventeenth Century, the person of the monarch and the role of monarch are considered to be separate. Whatever the constitutional rectitude of Elizabeth Windsor (which due to secrecy we must consider unproven) we cannot assume the same of Prince Charles. To swear allegiance to the person of Elizabeth and her heirs and successors is heinous. We can only hope that if there should arise an occasion when the monarch behaves in a grossly unconstitutional manner then our representatives will take this as releasing them from their oaths.
In reality, we must end this ridiculous anachronistic charade and bring our constitution up to date. The post Brexit hiatus, especially over the wrangling surrounding the arrangements for triggering EU Article 50 means we cannot rely on these constitutional gossamers. We must install a properly accountable Head of State who is genuinely responsible to all of us. In this case the Windsors have proved impotent to facilitate political solutions in a perilous power vacuum. but we cannot assume they will not seek to take advantage of future constitutional impasses. The oath MUST be replaced by an oath to the people!