Photograph courtesy of Zak Bratto

Around 2,300 years ago, in book three, chapter five of his weighty tome De Anima, Aristotle introduced the concept of the agent intellect, a second intellect that hovers somewhere between the soul and the divine. It was a controversial idea, partly because no one really understood what the philosopher was banging on about, and mostly because many suspected it was utter codswallop.

However, the agent intellect provides a powerful lesson that has withstood two millennia - for all the advances in modern neuroscience, there is still little understanding about how the mind works beyond a basic insight into neural networks and functional anatomy.

The Agent Intellect is also the title of the third album by Detroit's Protomartyr and the starting point for lyrical themes that dominate the record. It's an album of rugged post-punk that centres on the emotional punch provided by singer and lyricist Joe Casey. Much of The Agent Intellect explores the concept of the mind, and the impact of its debilitation through internal and external factors.

It's a marvellous record and the band's third in three years, as Casey makes up for a late start to his music career. Protomartyr formed in 2008 after Casey - then in his mid-30s and wanting to do something other than work "shitty" jobs and "watch TV all day" - hooked up with guitarist Greg Ahee and drummer Alex Leonard (bassist Scott Davidson would join later and complete the line-up) and badgered them into letting him sing over their music, eventually making their way to 2014's breakthrough album, Under Color Of Official Right, which showcased a jagged guitar sound (think The Fall, Big Black and Pere Ubu) and Casey's mournful baritone coupled to his cuttingly insightful lyrics.

When Joe and I talk, we reflect on a common sadness in our lives - both our mothers suffer from Alzheimer's disease. We have both endured the pain of watching a person we love dearly lose the very core of their personality as their mind slowly erodes. As our mothers' condition deteriorates, it is depressingly easy to deduce that their 'self' - what makes them who they are - is slowly disappearing.

The penultimate track on The Agent Intellect is 'Ellen', named after Joe's mother, on which Casey celebrates her past without resorting to maudlin gloom. Perhaps Protomartyr's finest work to date, 'Ellen' is a beautiful and brave song and a poignant reminder of the fragile nature of the mind.

Prior to Protomartyr, Greg and Alex were in a band called Butt Babies. What was it about the band that made you want to work with them?

Joe Casey: Not the name, that's for sure. I first started hanging out with Greg and Alex because we worked the same job. Initially, I didn't actually know that they were in a band called Butt Babies. What I liked about them was that they were good at what they did and they had a noticeable enthusiasm when they were playing. In addition, they were fun guys to hang out with. I figured there was only a guitar player and a drummer, and while they both sang, maybe I would see if they would let me sing on a couple of songs. But, yeah, if I had heard the name Butt Babies from the get-go, I might not have approached them.

You started Protomartyr in your mid-30s and the other band members are ten years your junior. What made you decide to begin making music at such - and I say this as someone much older than you - an 'advanced' age??

JC: Well, I am from Detroit and many of my friends and I have shitty jobs. They may work at a store, or be a bartender. I've worked as a doorman and at an old folks' home. So, when I was thinking about starting a band, it wasn't as if I had a career I was pursuing or any kind of wealth. I needed to fill my time, rather than sitting around and watching TV. I had friends in bands, so it wasn't too much of a leap to think of being able to practice in a basement or a garage and then play in a bar.

Did you have an idea what you wanted Protomartyr to sound like and, if so, how different was that to the music Butt Babies were making?

JC: What happened was that we would have beers and hang out. The guys would play their music and I would try to sing over it. We'd be pretty drunk and it was a case of: "Why not form a band?" Everyone has a fantasy of what they want their band to sound like. However, because I knew nothing about making music, I was unable to describe what I wanted properly. So, a third sound was created, which wasn't exactly what I had envisaged but the guys were getting something out of it. I wanted us to sound like old Fall records, but I could work with what they were giving me.

Was The Fall your only point of reference?

JC: No, I was really inspired by a small label called Hyped To Death that was collecting all these British post-punk records and putting them out under the Messthetics series. The CDs would have 30 songs from 30 different bands and each song sounded different. Each song sounded incompetent as well as sounding brilliant. That was attractive - as it meant it was okay if we were incompetent and that we could try different sounds on different songs. It wasn't about ripping off a particular song, or a specific sound, but more about tapping into the spirit of what I heard on those records.

Turning to the album, The Agent Intellect is named after a somewhat controversial theory put forward by Aristotle. What was it about this theory that resonated with you?

JC: I had a read about it a little. When I was first thinking about the album, I wasn't thinking much more than that the "agent intellect" was an old-time term for the thought process. However, the more I thought about it, and as I begin to collate the songs in my notebook, I realised that all the songs were about how the mind works and how it can be attacked from the outside and the inside. Then I began to read more about the agent intellect and more about Aristotle and the fact that few people really understood what he meant. For me, that became a great metaphor for the mind itself. No one really knows how the brain works and what makes you 'you' and me 'me'. It was lucky I plucked it out of a book because I thought it sounded cool, because that concept applies to much of what these songs are about.

Like you, my mother suffers from Alzheimer's disease. It's been horrific to see her personality disappear as her condition has deteriorated. It has made me think a lot about the relationship between the person and the mind. Did your mother's illness impact the way you approached the themes on The Agent Intellect?

JC: Yes. My mother's Alzheimer's informs how I think about the concept of the mind and - as you know - it is incredibly frustrating to see someone completely change. It's like sand going through an hourglass. It is constantly happening in front of you. When my dad died, it was a life-changing moment for me. When a parent dies it is incredibly hard, but, now, in retrospect, my dad was walking around like a normal person and three days later he was dead. It was very sudden. With something like Alzheimer's it is worse because my mom is still alive and she is still my mother, but it is a much slower process.

How did you approach writing lyrics about such a personal subject?

JC: When it came to the lyrics, I didn't want people to accuse me of being really depressive. I really tried to fight against that and not have a complete downer about the subject. There is really only one song that is about mom - and that's 'Ellen'. I did want to address my mom's situation, but I didn't want to be maudlin about it and I loved the music that the guys had written [for the song]. I kind of knew not to do a typical Protomartyr thing or mumble a bunch of shit, or to make it too dramatic or too bombastic.

So, how difficult was it for you to find the words to 'Ellen'?

JC: I didn't want to be too clinical or too personal, or talk about specifics about my mom's story. Therefore, what worked for me was to write a song about what my mom was going through and about time itself, removing the person from the subject matter, even if the song is named after her. It becomes more universal and more about the passage of time and that time will keep moving whether we want it to or not, and that we have to embrace that fact.

For me, your words are a big feature of Protomartyr's allure. Is lyric writing an easy process for you?

JC: It doesn't come naturally and it's the aspect of the band that I invest most energy in. It's the reason I am in a band. I'm definitely not in a band to convince anyone I can sing. I never have any pre-written lyrics that I want the guys to write a song about. The music is first and I have to fit something into that structure. Trying to do that is the hard part of being in the band, but it is a great privilege to be able to devote so much time to worrying about what I am yelling.

I believe you initially suffered from stage fright quite badly. Have you overcome that particular fear?

JC: It's less now than it was, but I am glad it is still there. I never want to be completely comfortable on stage - it's a weird place to be to have everyone staring at you. I still take my glasses off so I can't see anything. I had nervousness within me since before I was in a band - I'm kind of a nervous character - so having that heightened on stage helps me as the fear gives me focus. I am used to that being the case - and the nervousness gives me an edge that I need and makes things interesting.

With that in mind, how is the touring experience for you? Is it something you enjoy?

JC: You don't want to complain about it. Touring is exciting, fun and the reason why you want to be in a band. Touring Europe - which we did last year and are about to again - was hitting one of our main goals for starting a band. However, touring is all about trying to find a place to take a shit each day.

I'm thinking that would be a huge concern for me.

JC: Well, if you want to play a cool punk club, that's great - but punk clubs don't have any toilet seats. After a while, little things like that become big issues.

I can imagine. I'm done with my questions - I'd just like to thank you for your time and for talking to me about your mother's illness. I know it is a difficult thing to discuss.

JC: Thank you. I did think that once I put it out there, people are going to want to talk about it. I think it is probably better to talk about it than not talk about it. If mom had her wits about her, she'd probably be very embarrassed but I think with something like Alzheimer's we have to talk about it and shine some light on the disease.

The Agent Intellect is out now on Hardly Art. Protomartyr continue their UK tour with METZ tonight at The Fleece in Bristol; for full details and tickets, head here