From Companion to Gaelic Scotland –

“The most famous of the eighteenth-century Gaelic poets. He came of a notable Gaelic family; he was a great-grandson of Ranald MacDonald of Benbecula and of Mary, daughter of Angus MacDonald of Islay (so claiming descent from King Robert II). Flora MacDonald of the ’45 was his first cousin. His father, Maighstir Alasdair, was minister of Eilean Fhionain (graduated University of Glasgow, 1674). Alasdair is thought to have been a student there too, and he set some of his poems to airs played on the bells in the Tolbooth Steeple, not far from the Old College. [...] It may be that an early marriage, to Jane MacDonald of Dalness, interfered with his studies.

“We find mention of him in records from 1729 onwards, as SSPCK teacher and catechist, in Eilean Fhionain first, later in Coire a’ Mhuilinn in Ardnamurchan. In 1744 his son Ranald is acting as his substitute in Coire a’ Mhuilinn, Alasdair having ‘deserted’ his post to help rally the Jacobite clans. He held a Captain’s commission in Prince Charlie’s army and is almost certainly the author of the Journal and Memoirs of P— C— 1745–46; from one or two references there it could be thought that he had taken part in the ’15 also.

“Mac Mhaighstir Alasdair’s collection of poems, Ais-eiridh na Sean Chànoin Albannaich, was the first secular printed work in Gaelic (apart from his Vocabulary of 1741). [...]

“He was a man of strong views and violent emotions but with a hard intellectual cast of mind also; he was learned in the Gaelic tradition and open to influence from his other reading; he was an innovator and a conservative; and his poetry is full of the stimulating contraditions that proceed from these diversities.”