Suggesting that natural products or ingredients are inherently superior to those that are synthetic is a common flaw in reasoning used by influencers, brands and politicians alike.

Before writing this column, I had a hair appointment. As my stylist fastened the smock cape around my neck, she gestured to the shampoo she'd use. "It's a new line, made from 90% natural ingredients," she explained. The accompanying pamphlet, contained short descriptions of each product – one shampoo used prickly pear extract, another acai berries. A third incorporated chia seeds.

When I got home – purchased shampoo bottles in hand – I took a closer look at the ingredient list. Cetearyl alcohol, glycerin, behentrimonium chloride, isopropyl myristate. All common, laboratory-made ingredients. None worried me. But none of which, despite being used in far greater quantities than any of the fruit extracts, were highlighted in the brand's adverts.

The tactic that had been used – perhaps successfully, in my case – is hundreds of years old. It is often deployed on social media, by brands and influencers, and by politicians around the globe.

Often called an "appeal to nature", or the "naturalistic fallacy", it is one of the most commonly-seen types of logical fallacies, or flaws in reasoning that can make a claim sound surprisingly convincing. Anytime you hear someone make a claim that a product or practice is superior because it is "natural", or that one is inferior (or even harmful) because it is not "natural", this is the naturalistic fallacy at work. So are arguments that something is "as nature intended", or that something is bad specifically because it is a "chemical" or "synthetic".

Nature is, in many ways, wonderful. And it has a great deal to teach us. So why isn't it true that something is better merely because it comes from nature?

For one thing, because nature, of course, does not have intentions – not in any conscious sense. As such, nor does it have intentions to be good, or to help humans, specifically.

We don't need to get too philosophical to grasp this. Just consider a handful of nature's creations. Arsenic, which can kill an adult with a dose as little as 70mg, is natural. So is asbestos, which causes cancer. Cyanide, which can kill with as little as 1.5mg per kilogram of body weight if ingested, is a phytotoxin produced, naturally, by more than 2,000 different plant species, including almonds, apricots and peaches. This is also why some "natural" remedies frequently marketed – such as ground apricot seeds – can in fact be dangerous to consume.

And this is the trouble with the use of the word natural that is so commonly used to market products. It is a poorly defined term that doesn't necessarily mean the product labelled as such will be better for you, or indeed safer, than any other alternatives.

One investigation of teething products for babies labelled as "natural" found, for example, that more than 370 infants experienced adverse events such as seizures or delirium. The products were found to........

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