Steven Wise has spent much of his life trying to convince a sceptical world that chimpanzees should have legal rights, such as the right to be free.
The US lawyer, professor, author and animal rights campaigner, who is visiting Australia on a lecture tour, says that, when he started out 30 years ago, society thought he was ridiculous.
But the mood is changing and now the US courts are taking him seriously, while about 140 law schools in the US are teaching animal rights law.
His journey started in 1979 when someone gave him Animal Liberation by Australian philosopher Peter Singer.
"The first time I opened this book up, I said, holy smoke, I had no idea we are treating animals this way," he told The New York Times..
"I began in this area in 1981. People laughed at me and they barked when I walked into a courtroom."
Professor Wise is president of a not-for-profit organisation called the Nonhuman Rights Project (NhRP). He calls himself an "animal-slave lawyer" and says his detractors, mainly creationists, have accused him of being "chimpocentric".
In the US in the 1700s, human beings could be slaves, treated as "things" in the eyes of the law.
In the US, and the rest of the world, right now, animals are treated as "things", not "persons", and have no rights – for example, the right to be free. In law, not being a "legal person" prevents animals from having rights and so permits them to be misused and abused.
Professor Wise is on a mission to change that.
"At one time, not all human beings were considered 'persons' – children, women and slaves were simply the property of men," he says.
"We're saying that, based on clear scientific evidence, it is time to take the next step and recognise that certain animals cannot continue to be exploited as property."
The answer might begin to become clearer this month when officials from a New York university are due to show cause in court why they should not release two chimpanzees they have in detention.
Professor Wise's "clients" are young males Hercules and Leo, who are being held at Stony Brook University, where they are being used for experiments on how humans came to walk upright.
His group is asking courts in the US to recognise that certain animals, which have complex cognitive abilities, should be entitled to basic legal rights.
He wants the chimps released into the care of Save the Chimps, a sanctuary in Florida.
The group is focusing on securing limited legal personhood only for the great apes, dolphins, whales and elephants that Professor Wise considers to have "autonomy" and "self-determination".
Granting chimpanzees (or any other animal) legal personhood would not mean they're regarded as human beings under the law, nor that they would be granted human rights (such as the right to vote or free speech).
As legal persons, they would be entitled to the fundamental rights that are appropriate to their species, such as the right to bodily liberty and bodily integrity, which includes protection from medical procedures for scientific research.
In 2013, the NhRP filed three habeas corpus lawsuits demanding limited personhood rights for four chimpanzees, including Tommy, a 26-year-old former circus performer who now lives in a cage in a used trailer lot.
On December 4 last year, the New York State Appellate Court decided that legal personhood could not be given to Tommy due to a lack of legal precedent, his supposed inability to assume legal responsibilities, and his species.
However, last month, Justice Barbara Jaffe, of the New York state Supreme Court, directed officials at Stony Brook University to show cause under a habeas corpus statute for holding Hercules and Leo, which only persons are currently entitled to.
The judge has not decided that the chimps are legal persons, but she clearly thinks that they might be and she wants to hear a full-scale argument on it.
The hearing, originally set down for Wednesday, will be held on May 27 after Professor Wise returns to the US.
The NhRP is seeking so-called "immunity rights" for the animals. They are basically rights to be left alone and are the same as the rights enjoyed by humans not to be enslaved.
Professor Wise says he is not asking for rights that come with corresponding claims, such as those under a contract, which would confer rights and duties on both parties.
No one argues that chimpanzees could enter into a contract, such as a sale, where one person agrees to hand over money and another person agrees to hand over the thing to be sold. Not even all humans have such rights – for example, children can't enter into contracts.
But chimpanzee rights – to be free and to live in a community of chimps – would protect chimpanzees, just as human rights protect people.
Similarly whale rights would be specific to cetaceans and have as a key component the right to swim freely in the oceans and not be hunted.
Professor Wise says that only in 2011 did money come in to hire staff; before that, everyone worked as volunteers.
Labelled "one of the pistons of the animal rights movement" by the Yale Law Journal, he has taught animal law at Harvard and other law schools and has written four books on the law and animal rights.
"The first 30 years were the toughest," he jokes.
Senior curator at Sydney's Taronga Zoo, Erna Walraven, responded: "Taronga applauds efforts to improve the principles and standards that underpin human care of great apes in general. However, this approach suggests a test case in which lawyers or courts attempt to codify what is "appropriate to their species", and this could unintentionally impose human paradigms that are not necessarily helpful. The zoo is advocating for a more considered approach for welfare legislation to be strengthened based on detailed knowledge of the complex behaviour and biology of the various great ape species, both in our care and in the wild.
"If the welfare of a single chimpanzee could be improved through any joint efforts, we would welcome the opportunity."
Professor Wise is the keynote speaker in this year's Animal Law Lecture Series, presented across Australia by animal protection institute Voiceless.
Professor Wise will be speaking in Brisbane on Sunday, Melbourne on Monday, Canberra on Wednesday and Perth next Monday.
