OF the many things we claim to have invented, perhaps the one that escapes everyone’s attention is the biggest, longest lasting and most influential intellectual innovation of them all.

No, not the television or the telephone or radar or penicillin or the tarmacadam road surface or the pedal bicycle or the pneumatic tyre or waterproof fabric or the vacuum flask or the steamboat or any number of engineering or medical developments created by Scots. No, this “invention” was common sense, the philosophy that influenced generations.

In this third and final part of a series on the Scottish Enlightenment, we will look at some of the personalities of that amazing period in Scottish history, having already considered two of the greats in David Hume and Adam Smith.

In no way does keeping the following people to the last in any way belittle them, for their achievements in their fields were every bit as important and fundamental as Hume’s philosophical advances and Smith’s creation of the science of political economy – common sense tells you that, and common sense was itself a product of the Scottish Enlightenment.

The “common sense” philosophy was devised principally by Thomas Reid, a remarkable figure who, in his heyday – the latter half of the 18th century – was more renowned and respected than Hume. And it was his retort to Hume’s sceptical empiricist philosophy that made him famous, as we shall see.

Reid was born in the village of Strachan near Banchory on the River Dee in Aberdeenshire on April 26, 1710. He was educated by his parents, Lewis and Margaret, at home as well as in the local parish school. He entered Marischal College, now part of Aberdeen University, from where he graduated at the age of 16 in 1726.

Reid then began to study theology and in 1737 he became a minister in the Church of Scotland, serving first in the New Machar parish 10 miles from Aberdeen while retaining his links to that city He married his cousin Elizabeth Reid – they would go on to have nine children – and he appears to have been very happy with parish and home life. However, his questing mind could not be sated and he returned to academia as professor of philosophy at King’s College, which would later join Marischal to become the University of Aberdeen. Most people accept that the university dates from the foundation of King’s in 1496 rather than the union of the colleges in 1860, and thus Aberdeen is the third-oldest university in Scotland and the fifth-oldest in the UK and indeed all English-speaking countries.

In 1739, Hume had published his A Treatise on Human Nature in which he expressed his theory that all human knowledge derives from experience, and that book can be seen as the start of the Scottish Enlightenment simply because of the massive debate that it started.

Reid had been developing theories of his own and they were contrary to those of Hume. He took his time to develop his arguments, famously doing so in a series of graduation addresses that formed the basis of his book An Inquiry into the Human Mind on the Principles of Common Sense that was published in 1764.

In the current Encyclopaedia Britannica – a publication that began in Edinburgh during the Enlightenment – there is a succinct summary of Reid’s position against Hume: “Lengthy studies convinced Reid that Hume’s scepticism was incompatible with common sense, for both human behaviour and the use of language provide overwhelming evidence to support such truths as the existence of a material world and the retention of personal identity in the midst of continuous change.

“Unable to find fault with Hume’s argumentation, Reid settled on Hume’s ‘theory of ideas’ as the prime source of error. Rejecting the notion that ideas are the direct object of the mind’s awareness, Reid substituted a view of perception in which sensations ‘suggest’ material objects. For him, this ambiguous assertion solved the problem.”

It was Reid’s genius that he expressed his ideas about the sensus communis – a term borrowed from Cicero – in plain and straightforward terms: “If there are certain principles, as I think there are, which the constitution of our nature leads us to believe, and which we are under a necessity to take for granted in the common concerns of life, without being able to give a reason for them; these are what we call the principles of common sense; and what is manifestly contrary to them, is what we call absurd.”

In the battle of common sense against the philosophers, Reid fixed his flag to the mast: “In this unequal contest betwixt common sense and philosophy, the latter will always come off with both dishonour and loss; nor can she ever thrive till this rivalship is dropped, these encroachments given up, and a cordial friendship restored: for in reality common sense holds nothing of philosophy, nor needs her aid. But, on the other hand, philosophy (if I may be permitted to change the metaphor) has no other root but the principles of common sense; it grows out of them, and draws its nourishment from them: severed from this root, its honours wither, its sap is dried up, it dies and rots.”

HIS challenge was direct: “Let scholastic sophisters entangle themselves in their own cobwebs; I am resolved to take my own existence, and the existence of other things, upon trust; and to believe that snow is cold, and honey sweet, whatever they may say to the contrary. He must either be a fool, or want to make a fool of me, that would reason me out of my reason and senses.”

These following words of his were not appreciated by Hume: “I confess I know not what a sceptic can answer to this, nor by what good argument he can plead even for a hearing; for either his reasoning is sophistry, and so deserves contempt; or there is no truth in the human faculties, and then why should we reason?”

By the 1760s, clubs were being established in Scotland’s main centres of population simply to discuss ideas and philosophy – the Select Society and the Poker Club in Edinburgh and many similar organisations attached to the universities joined thinking and, it must be admitted, drinking in a heady brew.

It greatly helped the development of the Enlightenment that rather a lot of Scotland’s aristocratic ruling classes had gone south to London to be at court or attend parliament so, with few exceptions, the Scottish Enlightenment was not garlanded with lordships but with professional people such as lawyers, lecturers, Kirk ministers and writers.

Into the debate came Reid with his own epistemology or theory of knowledge. He moved south to Glasgow University – he stayed in the city for the rest of his life – and succeeded none other than Adam Smith as professor of moral philosophy.

It is interesting to note that Reid’s ideas were spreading far and wide, and when Thomas Paine in America started writing a hugely influential pamphlet called Plain Truth, he read Reid’s material and changed its name. We know it now as Common Sense, and it really did help change the world as it influenced American and French revolutionaries.

Yet again, Reid took his time and developed his own ideas, which were published under the title Essays on The Intellectual Powers of Man (1785) and Essays on the Active Powers of the Human Mind, published in 1788 when Reid was 78.

They contain Reid’s deepest thoughts, with this from the Intellectual Powers: “Every man feels that perception gives him an invincible belief of the existence of that which he perceives; and that this belief is not the effect of reasoning, but the immediate consequence of perception.

“When philosophers have wearied themselves and their readers with their speculations upon this subject, they can neither strengthen this belief, nor weaken it; nor can they show how it is produced.

“It puts the philosopher and the peasant upon a level; and neither of them can give any other reason for believing his senses, than that he finds it impossible for him to do otherwise.”

Language itself could be a difficulty for the common-sense philosopher: “There is no greater impediment to the advancement of knowledge than the ambiguity of words.”

Reid also nailed the difficulty of debating: “Before men can reason together, they must agree in first principles; and it is impossible to reason with a man who has no principles in common with you.”

Reid was lauded for his common-sense philosophy, and he had powerful allies during his time at Glasgow, where he taught until retiring at the age of 70 in 1781 – as you will have deduced, he retired to write more of his thoughts down on paper, finally dying in Glasgow in 1796, lauded for his contributions to philosophy that influence people even to this day.

By then, Adam Ferguson, professor of moral philosophy at Edinburgh, was in the process of becoming the “father of modern sociology”. Another great figure of the Enlightenment, Professor (later Sir) Dugald Stewart, was Reid’s pupil at Glasgow and he succeeded Ferguson – the Scottish Enlightenment was rather a small world in some ways.

There is simply not enough space in 10 Nationals to list all the figures of the Scottish Enlightenment so here are thumbnail sketches of the ones you should learn about – try Google, or better still, go to some of our best libraries such as the Mitchell in Glasgow, Central Library in Edinburgh and the National Library itself.

George Campbell, also a Kirk minister, who died in the same year as Reid, made rhetoric his field in which he was unsurpassed. James Beattie (1735-1803) was a poet and a philosopher who argued cogently against slavery.

IN literature, leaving aside James Macpherson because he faked the Ossian legend, there was James Boswell (1740-1795) an Edinburgh lawyer who practically invented the science of biography with his works on Samuel Johnson.

Allan Ramsay (1713-1784) was the portrait painter son of the poet also named Allan (1686-1758) and both made crucial contributions to Scottish culture.

Hugh Blair was another Kirk minister who was a central figure in the Enlightenment due to his gregarious personality and his thoughts on writing. Of course the greatest individual product of that whole era in Scotland was Robert Burns (1759-1796) about whom nothing more need be said.

In future editions of this column we are going to look at numerous figures from the world of science, so we will set aside Lord Monboddo, James Hutton, and Joseph Black.

I am also planning a special look at the Adam family and the Edinburgh New Town architect James Craig, but what I would really like is for everyone reading this column to make their own investigation into the period 1740-1820 in Scotland, a time we really did lead the world in many areas. Go on, Enlighten yourselves.

I have said before and will repeat it again: it is a time for a new Scottish Enlightenment to once again make ideas and innovation the weapons that we use to confront the future in a world that has never needed common sense more than it does now.

It is time for a Scottish Manifesto, one that emphasises reason and independence of mind, and which will show that Scotland needs to stand alone and make its own choices. You know what? I might just have to write it myself.