To split or not to spilt, that is the question. If the object of splitting is an infinitive, my rule is simple – split it or don’t split it, but have an eye to ambiguity, to the verb you want to qualify, and to euphony. Nobody in her right mind would correct the world’s most famous split infinitive, that of Starship Captain James T Kirk, because to do so would be to disturb its ringing prosody, even though its sense would be as solid as a rock despite the change.
If all fails, say it another way.
Henry Watson Fowler is often granted the last word on the subject, and I’m going to quote him in full here, not because I regard him as authoritative, but because this is one of the wittiest pieces of writing on the subject. I chuckle to myself whenever I get to the place where he uses ‘readier’ and I want to yell “More readily!” – I suspect that he did that deliberately. Although he does come down very heavily against avoidance of the split infinitive where such avoidance is obsessive to the point of fetishistic, he is gracious enough to quote one of the ugliest splittings ever.
Let me give you a word of warning – don’t use Fowler, or any other source, as a bolster for your own prejudices. ‘Magister ipse dixit’ is never a good argument. I try not to, and I’m one of the most consistent contributors to grammar debates on Facebook that I know; I find them difficult to resist. Here he goes:
The English-speaking world may be divided into (1) those who neither know nor care what a split infinitive is; (2) those who do not know, but care very much; (3) those who know and condemn; (4) those who know and approve; and (5) those who know and distinguish.
(1) Those who neither know nor care are the vast majority, and are a happy folk, to be envied by most of the minority classes. ‘To really understand’ comes readier to their lips and pens than ‘really to understand’; they see no reason why they should not say it (small blame to them, seeing that reasons are not their critics’ strong point), and they do say it, to the discomfort of some among us, but not to their own.
(2) To the second class, those who do not know but do care, who would as soon be caught putting their knives in their mouths as splitting an infinitive but have only hazy notions of what constitutes that deplorable breach of etiquette, this article is chiefly addressed. These people betray by their practice that their aversion to the split infinitive springs not from instinctive good taste, but from tame acceptance of the misinterpreted opinion of others; for they will subject their sentences to the queerest distortions, all to escape imaginary split infinitives. ‘To really understand’ is a s.i.; ‘to really be understood’ is a s.i.; ‘to be really understood’ is not one; the havoc that is played with much well-intentioned writing by failure to grasp that distinction is incredible. Those upon whom the fear of infinitive-splitting sits heavy should remember that to give conclusive evidence, by distortions, of misconceiving the nature of the s.i. is far more damaging to their literary pretensions than an actual lapse could be; for it exhibits them as deaf to the normal rhythm of English sentences. No sensitive ear can fail to be shocked if the following examples are read aloud, by the strangeness of the indicated adverbs. Why on earth, the reader wonders, is that word out of its place? He will find, on looking through again, that each has been turned out of a similar position, viz between the word be and a passive participle. Reflection will assure him that the cause of dislocation is always the same — all these writers have sacrificed the run of their sentences to the delusion that ‘to be really understood’ is a split infinitive. It is not; and the straitest non-splitter of us all can with a clear conscience restore each of the adverbs to its rightful place: He was proposed at the last moment as a candidate likely generally to be accepted. / When the record of this campaign comes dispassionately to be written, and in just perspective, it will be found that … / New principles will have boldly to be adopted if the Scottish case is to be met. / This is a very serious matter, which dearly ought further to be inquired into. / The Headmaster of a public school possesses very great powers, which ought most carefully and considerately to be exercised. / The time to get this revaluation put through is when the amount paid by the State to the localities is very largely to be increased.
(3) The above writers are bogy-haunted creatures who for fear of splitting an infinitive abstain from doing something quite different, i.e. dividing be from its complement by an adverb; see further under POSITION OF ADVERBS. Those who presumably do know what split infinitives are, and condemn them, are not so easily identified, since they include all who neither commit the sin nor flounder about in saving themselves from it — all who combine a reasonable dexterity with acceptance of conventional rules But when the dexterity is lacking disaster follows. It does not add to a writer’s readableness if readers are pulled up now and again to wonder — Why this distortion? Ah, to be sure, a non-split die-hard! That is the mental dialogue occasioned by each of the adverbs in the examples below. It is of no avail merely to fling oneself desperately out of temptation; one must so do it that no traces of the struggle remain. Sentences must if necessary be thoroughly remodelled instead of having a word lifted from its original place and dumped elsewhere: What alternative can be found which the Pope has not condemned, and which will make it possible to organise legally public worship ? / It will, when better understood, tend firmly to establish relations between Capital and Labour. / Both Germany and England have done ill in not combining to forbid flatly hostilities. / Every effort must be made to increase adequately professional knowledge and attainments. / We have had to shorten somewhat Lord D——’s letter. / The kind of sincerity which enables an author to move powerfully the heart would … / Safeguards should be provided to prevent effectually cosmopolitan financiers from manipulating these reserves.
(4) Just as those who know and condemn the s.i. include many who are not recognisable, since only the clumsier performers give positive proof of resistance to temptation, so too those who know and approve are not distinguishable with certainty. When a man splits an infinitive, he may be doing it unconsciously as a member of our class 1, or he may be deliberately rejecting the trammels of convention and announcing that he means to do as he will with his own infinitives. But, as the following examples are from newspapers of high repute, and high newspaper tradition is strong against splitting, it is perhaps fair to assume that each specimen is a manifesto of independence: It will be found possible to considerably improve the present wages of the miners without jeopardizing the interests of capital. / Always providing that the Imperialists do not feel strong enough to decisively assert their power in the revolted provinces. / But even so, he seems to still be allowed to speak at Unionist demonstrations. / It is the intention of the Minister of Transport to substantially increase all present rates by means of a general percentage. / The men in many of the largest districts are declared to strongly favour a strike if the minimum wage is not conceded.
It should be noticed that in these the separating adverb could have been placed outside the infinitive with little or in most cases no damage to the sentence-rhythm (considerably after miners, decisively after power, still with clear gain after be, substantially after rates, and strongly at some loss after strike), so that protest seems a safe diagnosis.
(5) The attitude of those who know and distinguish is something like this: We admit that separation of to from its infinitive is not in itself desirable, and we shall not gratuitously say either ‘to mortally wound’ or ‘to mortally be wounded’, but we are not foolish enough to confuse the latter with ‘to be mortally wounded’, which is blameless English nor ‘to just have heard’ with ‘to have just heard’, which is also blameless. We maintain, however, that a real s.i., though not desirable in itself, is preferable to either of two things, to real ambiguity, and to patent artificiality. For the first, we will rather write ‘Our object is to further cement trade relations’ than, by correcting into ‘Our object is further to cement …’, leave it doubtful whether an additional object or additional cementing is the point. And for the second, we take it that such reminders of a tyrannous convention as ‘in not combining to forbid flatly hostilities’ are far more abnormal than the abnormality they evade. We will split infinitives sooner than be ambiguous or artificial; more than that, we will freely admit that sufficient recasting will get rid of any s.i. without involving either of those faults, and yet reserve to ourselves the right of deciding in each case whether recasting is worth while. Let us take an example: ‘In these circumstances, the Commission, judging from the evidence taken in London, has been feeling its way to modifications intended to better equip successful candidates for careers in India and at the same time to meet reasonable Indian demands.’ To better equip ? We refuse ‘better to equip’ as a shouted reminder of the tyranny; we refuse ‘to equip better’ as ambiguous (better an adjective?); we regard ‘to equip successful candidates better’ as lacking compactness, as possibly tolerable from an anti-splitter, but not good enough for us. What then of recasting? ‘intended to make successful candidates fitter for’ is the best we can do if the exact sense is to be kept, it takes some thought to arrive at the correction; was the game worth the candle?
After this inconclusive discussion, in which, however, the author’s opinion has perhaps been allowed to appear with indecent plainness, readers may like to settle the following question for themselves. ‘The greatest difficulty about assessing the economic achievements of the Soviet Union is that its spokesmen try absurdly to exaggerate them; in consequence the visitor may tend badly to underrate them.’ Has dread of the s.i. led the writer to attach his adverbs to the wrong verbs, and would he not have done better to boldly split both infinitives, since he cannot put the adverbs after them without spoiling his rhythm? Or are we to give him the benefit of the doubt, and suppose that he really meant absurdly to qualify try and badly to qualify tend?
It is perhaps hardly fair that this article should have quoted no split infinitives except such as, being reasonably supposed (as in 4) to be deliberate, are likely to be favourable specimens. Let it therefore conclude with one borrowed from a reviewer, to whose description of it no exception need be taken: ‘A book … of which the purpose is thus — with a deafening split infinitive — stated by its author: “Its main idea is to historically, even while events are maturing, and divinely — from the Divine point of view — impeach the European system of Church and States”.’
A Dictionary of Modern English Usage.