I searched for an té ná fuil láidir ní foláir dó bheith glic, which came up in Aesop 47, on the Internet, to see if this phrase had any less literal translation that captured the meaning in truly colloquial English, and found a page on Daltaí discussing it. On that page, the phrase is given, incorrectly, as an té nach bhfuil láidir ní folair dó a bheith glic.
It goes on to say:
The phrase a bheith glic means “to be clever.”
But there is no infinitival particle in Irish. PUL was very insistent on this point. “To be clever” is just bheith glic, not a bheith glic. This is a common misconception about the Irish language.
The phrase is an té ná fuil láidir ní foláir dó bheith glic, but as I am editing Aesop a Tháinig go hÉirinn into the Muskerry House Style used by the Coiste Litriochta Mhúscraí, the dó is edited as do, as dó (“to him”) is pronounced with a short /o/ in Muskerry Irish. Unfortunately, this yields ní folair do bheith glic, where someone might think that the do was an infinitival particle governing bheith, but it is not for the reason stated above. It is also unfortunate that the Muskerry House Style uses do for both dó and do, when the former is pronounced /do/ and the latter /də/. One way of showing the short /o/ that has been used in the past is to use a grave accent: ní foláir dò bheith glic.
On the point of the lack of an infinitival particle, in Papers on Irish Idiom, p74, PUL discusses the way grammar books say:
Infinitive Mood: do bhualadh, to strike.
And many learners then proceed to translate “I wish to walk” as is maith liom do shiúl.
Now I have, once for all, to tell Irish learners that Irish of that sort is not Irish at all. I need not tell it to people who have spoken Irish all their lives. They would never dream of saying, Is maith liom do shiúl, as Irish for “I wish to walk”. They would say at once, Is maith liom siúl. If one of them were to translate into English the sentence Is maith liom do shiúl, he would, after a pause, perhaps, say, “I like your walk”. He would give to do the only possible sense which it can have in that sentence. It has not the remotest connection with the English “to”, nor the faintest shadow of its meaning.
The a in Daltaí’s a bheith is just as wrong as saying do bheith. They would imagine there is an infinitival particle in Irish, and that it can be either do or a, with a a weakened form of do, but that is not the case. A bheith means “its being” or “his being”.
The idea there might be an infinitival particle in Irish may derive from the proleptic use of a in some sentences, e.g. d’iarras ort a rá leis gan teacht, “I asked you to tell him not to come”, but here a rá is proceded by a possessive particle, “its telling”, where the a refers in advance to the telling of him not to come.
A bheith glic on the Daltaí page is not proleptic, but rather an incorrect insertion of an infinitival particle that does not exist in Irish. The pronunciation shown on that page is also wrong, as if /do:/ is followed by /ə/ before the /vʹeh glʹikʹ/. Fortunately, the sound file on that page, if listened to, will show there is no /ə/.