Can you explain the Trinity to me?

[Mayor] 'Can you explain the Trinity to me? It was more than they could do in Salamanca.'

[Monsignor Quixote] 'I can try.'
'Try then.'
'You see these bottles?'
'Of course.'
'Two bottles equal in size. The wine they contained was of the same substance and it was born at the same time. There you have God the Father and God the Son and there, in the half bottle, God the Holy Ghost. Same substance. Same birth. They’re inseparable. Whoever partakes of one partakes of all three.'
'I was never even in Salamanca able to see the point of the Holy Ghost. He has always seemed to me a bit redundant.'
'We were not satisfied with two bottles, were we? That half bottle gave us the extra spark of life we both needed. We wouldn’t have been so happy without it.'
....

'May God forgive me,' Father Quixote said,  'for I have sinned.'
'It was only a joke, father. Surely your God does understand a joke.'
'I have been guilty of heresy,' Father Quixote replied. 'I think - perhaps - I am unworthy to be a priest.'
'What have you done?'
'I have given wrong instruction. The Holy Ghost is equal in all respect to the Father and the Son, and I have represented Him by this half bottle.'
'Is that a serious error, father?'
'It is anathema. It was condemned expressly at I forget which Council. A very early Council. Perhaps it was Nicaea.'
'Don’t worry, father. The matter is easily put right. We will throw away and forget this half bottle and I will bring a whole bottle from the car.'

G. Greene, Monisgnor Quixote (1982), 51-53