A mathematical equation can tell how much your partner loves you

How to PROVE your partner loves you: Scientist creates complex mathematical equation to sum up true love

  • It combines reasoning and probability – known as Bayesian probability theory 
  • It can tell if a relationship is based on ‘unconditional’ or ‘conditional’ love
  • Conditional love is any value from the equation between the value of 0 and 1
  • Unconditional love has a value of one and means no logic can change it 

A British scientist has created a complex mathematical equation to try and understand love.

Suki Finn, a postdoctoral research fellow in philosophy at the University of Southampton, has created a way to tell between unconditional and ‘conditional’ affection.

Her equation combines reasoning and probability – known as Bayesian probability theory – to help a person tell the condition of their relationship. 

Unconditional relationships have a solution of one which means no logic or rationale can sway a person’s answer.

Conditional love is any value from the equation between the value of 0 and one and is subject to change as a relationship progresses.

Dr Finn says that one type of love is not necessarily better than the other but that there are two very distinct forms of the emotion. 

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Suki Finn, a postdoctoral research fellow in philosophy at the University of Southampton, has created a way to tell between unconditional and ‘conditional’ affection (stock)

Dr Finn used the mathematical concept of Bayesian probability theory to help create the equation.

Bayesian probability theory creates a framework in which reasoning and probability are combined. 

Dr Finn said: ‘I will try to make sense of the confusing and complex emotion that we call love by creating a parallel between conditional/unconditional love and conditional/unconditional degrees of belief’. 


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As part of the process Dr Finn classified the ‘degrees of belief’ and gave them a value between 0 and one. 

As part of an in-depth feature in Aeon, the researcher explains that the value given to a person’s trait is not set in stone. 

She explains: ‘You could love her a little, at 0.3, or loads, at 0.9, for example.

‘Maybe you start at 0.3 and as you get to know his positive qualities (thus gaining information) your love grows to 0.9. 

‘Maybe she does something bad that hurts you (also providing more information) and as a result the love levels decrease.’

Unconditional relationships have a solution of one which means no logic or rationale can sway a person’s answer. Conditional love is any value from the equation between the value of 0 and one and is subject to change as a relationship progresses (stock)

WHAT IS THE EQUATION FOR UNCONDITIONAL LOVE?  

The formula for unconditional love is an adapted version of the maths for updating credences by conditionalisation.

This is: Crupdated(p)=Crinitial(p|e)

Cr is credence.

p is an event and Cr(p) is the probability – or ranking – of a trait between 0 and 1.

e is a proposition or event that counts as evidence that would alter a value- also known as a credence.  

Initial and updated refers to the before and after of the score when e is taken into account.

The line | simply mans ‘conditional upon’.

The rest of the proof is as follows:  

  • Cr(p|e) = Cr(e∩p)/Cr(e)
  • When Cr(p)=1, it is a theorem that Cr(e)=Cr(e∩p)
  • e is equivalent to (e∩p)∪(e∩¬p)
  • So Cr(e)=Cr(e∩p)+Cr(e∩¬p)
  • Cr(e∩¬p)=0
  • Cr(¬p)=Cr(e∩¬p)+Cr(¬e∩¬p)
  • Cr(p)=1 so Cr(¬p)=0
  • Cr(e∩¬p) and Cr(¬e∩¬p)
  • Cr(e)=Cr(e∩p)+Cr(e∩¬p) where Cr(e∩¬p)=0
  • Cr(e)=Cr(e∩p)
  • From Cr(e∩p)/Cr(e)
  • To Cr(e)/Cr(e)
  • To 1 (as anything divided by itself equals 1)
  • Crupdated(p)=Crinitial(p|e) 
  • Crinitial(p|e)=1
  • Crupdated(p)=1 when Crinitial(p)=1
  • Cr(e)≠0 

The researcher summed up the researcher and said: ‘Credence 1 is rationally unmovable, in a similar way to having unconditional love. 

‘And who said that there is no romance in maths?’

One indicates absolutely certainty and 0 indicates absolutely no certainty.        

If something is given a value of one a person’s resolve cannot get any stronger as it is considered to be an absolute certainty. 

‘No matter how strong the opposing information is, it will not detract you from credence 1, so the Bayesian says’, according to Dr Finn. 

In the research a value of one for the equation equates to unconditional love where, no matter the opposing logic, a person remains besotted. 

In contrast, conditional love sits between 0 and 1 and changes as a relationship develops.   

‘Unconditional love is love that will not change according to any information, as it was not built on the basis of information in the first place,’ Dr Finn said. 

‘This is love without reason, where no evidence or information can alter it. Why do you love someone? For no reason!’   

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