I think here 'reason' means the complete presence of awareness in a given moment. I have read some other of Marcus Aurelius' works and get a feeling that his usage of the word reason (which itself is a translation of some word in latin) is different from our usage of it (as of 2015). It probly means 'present moment awareness' or 'complete attention' or 'calm focus'.
![](http://pinterest.com/pin/create/button/?url=https://www.beameditator.com/2015/09/marcus-aurelius-on-being-in-here-and-now.html&media=https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjVCNlSex8-zEtNBezKkvcRoQosshaJFlTo9bZvf-2cP51Vx0fenmZs57ml2MXjWmcwjebxa_EtxJd38wq2l0DnunEU1dLJBlvTqaQMF633-lV9rZbKfdofGYdj3pETDSkKLjKFTiYcjKJL/s72-c/BeAMeditator-MarcusAurelius.jpeg&description= "Never let the future disturb you. You will meet it, if you have to, with the same weapons of reason which today arm you against...){kind=link}