The BBC has a report on human fertility that begins
It may be possible to one day create an "unlimited" supply of human eggs to aid fertility treatment, US doctors say.
I am no purist when it comes to splitting infinitives but this one grates horribly. There is no reason why it should not be written as
It may be possible one day to create an "unlimited" supply of human eggs to aid fertility treatment, US doctors say.
or
It may one day be possible to create an "unlimited" supply of human eggs to aid fertility treatment, US doctors say.
or
One day it may be possible to create an "unlimited" supply of human eggs to aid fertility treatment, US doctors say.
A split infinitive involves placing an adverb between the to and the infinitive proper. I would not write, but would not argue with, this:
It may be possible to even create an "unlimited" supply …
A split infinitive places the adverb immediately before the infinitive. This word is morphologically identical to the finite form used in the present. Adverbs are sometimes placed in this mid-position between subject or auxiliary and verb, so this is presumably the reason why a split infinitive often seems natural. We can say
… we even create …
so there is a certain naturalness to saying
… to even create …
But, and this is the point, we do not say
*If we one day create …
It is true that indefinite time adverbs can stand in mid-position, but only if they are one word. We say
We often create … / We will soon create …
but not
We every day create …
So, if it is accepted that a split infinitive is formed on the analogy of a mid-position adverb, this split infinitive is open to criticism because it has two words and is thus not truly analogous.
Apart from all that, there is another point: the adverbial phrase one day refers to the possibility rather than to the creation. It may be said that we are talking about the future possibility of one day creating human eggs. Then we could have
It may be possible to create one day an "unlimited" supply of human eggs to aid fertility treatment, US doctors say.
Personally, I don’t like this. I feel rather strongly, perhaps more than most, that adverbs have no business appearing between verb and object; and I can accept that my attitude comes from correcting so many Spanish speakers who create utterly impossible English sentences because that is a perfectly normal position for a Spanish adverb. Be that as it may, I still feel that the future idea expressed by one day goes with the possibility rather than the creation. Any future creation can only result from a future possibility. Thus, the primary future consideration is the possibility, and that is what should be modified by the adverb. This argument also applies to the form that I suggest above:
It may be possible to even create an "unlimited" supply …
Not only is this form
It may even be possible to create an "unlimited" supply …
more pleasant to my sense of language. It gets the also in the logical place as well.
